The Pope also held a service in the Vatican in which he lamented conditions for Palestinians in Gaza and called for the "clamour of weapons [to] cease" in Ukraine and other conflict zones.
Dame Sarah Mullally - the first woman to lead the Church of England in more than 1,400 years - was speaking in St Paul's Cathedral in her current role as Bishop of London.
"Many feel the weight of economic pressure. Some feel pushed to the margins," said the 63-year-old.
"Our national conversations about immigration continue to divide us, when our common humanity should unite us."
Families struggle to find secure housing, she added, while "our understanding of what it means to live and die well" is being challenged by the "complexities" of assisted dying.
Dame Sarah was elected in November and will legally begin her new role in January.
The Pope also gave his first Christmas Day sermon in the Vatican.
He said the story of Jesus's birth in a stable showed God "pitched his fragile tent" among the people of the world.
"How, then, can we not think of the tents in Gaza, exposed for weeks to rain, wind and cold?" said Leo.
The pontiff later toured the square in the "popemobile" before giving the traditional Urbi et Orbi (to the city and the world) blessing.
Speaking from the balcony of St. Peter's Basilica, he referenced conflicts in countries such as Sudan, Thailand and Cambodia - and said Ukrainians in particular had been "tormented by violence".
"May the clamour of weapons cease, and may the parties involved, with the support and commitment of the international community, find the courage to engage in sincere, direct and respectful dialogue," said the Pope.
The Archbishop of York, meanwhile, said in his own sermon that he had been "intimidated" by Israeli militias in the Holy Land earlier this year.
He called the visit "sobering" and said he was "stopped at various checkpoints and intimidated by local Israeli militias who told us that we couldn't visit Palestinian families in the occupied West Bank".
The Most Reverend Stephen Cottrell added: "The strangers we encounter in the homeless on our streets, refugees seeking asylum, young people robbed of opportunity and growing up without hope for the future, means that we are in danger of even failing to welcome Christ when he comes."
The King's Christmas message - recorded in Westminster Abbey - will be broadcast at 3pm. He and other members of the Royal Family attended church in Sandringham this morning.
His grandfather would visit and send him out to the mountains to cut down a pine tree. He would bring it home and small balls of cotton were hung on its branches.
In many countries, it's a familiar ritual: setting up and decorating a tree for Christmas Day. But in North Korea, December 25th is just another day and Christmas is effectively banned.
Ju said: "In my home, we just celebrated that kind of thing. But we didn't know what that day was about; just every December 25th, my grandfather asked us to do that.
"My grandfather taught us 'hey grandson, the other countries beside North Korea, every December 25th, they make this kind of tree and celebrate this day'."
Not knowing the origins of the tradition, his family displayed the tree openly.
The neighbours called it a "yolka" - a tree put up to mark the new year in the Russian-speaking world.
With Christianity being suppressed in North Korea, nobody knew the real origins of the tradition, and the family faced no repercussions, Ju said.
He explained: "It was possible because my village was a very small village. There were only 30 households living in my town, and it was very isolated from the main city."
The family would also clap and lead a chant. Its nonsense words sounded like "belly hem, belly hem, say goodbye, say goodbye".
What was the reason? Mysterious radio transmissions from across the border in South Korea offered a clue.
Those broadcasts would take Ju from the countryside of North Hamgyong Province to the White House.
"Me and my family actually listened to the illegal foreign radio broadcasting in North Korea," said Ju.
"We listened to the FEBC (Far East Broadcasting Company), which is South Korean Christian broadcasting. It's very clearly heard in North Korea in the very early morning.
"So that was the first moment that we heard about gospel and Christianity."
If the tree was tolerated, the radio was not.
Agents of the state would turn up unannounced and search the home, checking radios to see what frequency they were tuned into.
Ju said: "We had to risk our lives because we were listening to South Korean broadcasting that is highly prohibited in North Korea.
"If you get caught, you would go to political prison camp or even be executed, because it was Christian broadcasting.
"So every time we covered the window with a blanket and lowered the volume to prevent someone from hearing."
He continued: "That radio broadcasting was very impactful for my family.
"That radio was what motivated my father to escape from North Korea. He escaped first.
"When my father resettled in South Korea, he sent a broker to us. So me, my mother, and one of my sisters escaped in October 2009."
Escaping North Korea
Ju was just a child when he fled across the border to China, beginning a journey that would take him through three countries en-route to South Korea.
Staying at a missionary's house after crossing the frontier, he got some answers about this mysterious faith.
And on a cross-country bus through China, he embarked on a spiritual journey too.
He said: "On my bus, I did a sinner's prayer and received Jesus as a saviour."
Arriving in South Korea, where he can worship openly, Ju began to understand parts of his story in a new light.
That strange chant on Christmas Day?
"Belly hem was Bethlehem, and say goodbye was sacrifice," he said.
"My grandfather was trying to teach us about Christianity and Christmas Day."
He soon recognised other ways in which Christianity had breached the secure borders of North Korea.
He recalled a "funny story" told to him by a friend of his father about a man and woman in a garden.
"When I became a Christian, that story was exactly the same in the Bible," said Ju, now 29.
"That was actually the Garden of Eden, and Adam and and Eve's story."
Years later they were able to reach the man, still in North Korea, via a smuggled phone.
He revealed he was a missionary, who had converted to Christianity after crossing the border to China, and returned home to spread the gospel.
Ju knows only too well the risk he took in doing so.
He said: "My aunt and all of her family were sent to political prison camp, just because my aunt's grandfather-in-law was a Christian.
"When people get to that camp, they cannot come out until they die. So it's a slavery camp, and there is torture in there.
"We are still praying that my aunt's family are surviving there, but we cannot find them now."
Ju saw this tragedy play out again through his work with TIMJ, an organisation advocating for North Korean human rights.
"Some of the North Korean underground church members were working with us secretly," he said.
"A few of them got caught and sent to political prison camp, because they were caught sharing the gospel.
"Nobody knows whether they're alive or not."
Open Doors, a charity championing the cause of oppressed Christians worldwide, named North Korea as the country where believers face the most extreme persecution in 2025.
North Korea has topped the list every year since 2002, with the sole exception of 2022, when Afghanistan pushed it into second place.
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"I think it's because Juche ideology, which is North Korea's ruling ideology, has many similarities to the Bible," said Ju.
"So if you just erase god and put Kim Jong-un, Kim Jong-il, Kim Il-sung on there, that is Juche ideology.
"So when people know about Christianity, I think the North Korean government is afraid that people would know that Juche ideology is a lie."
Meeting Trump
It's a message that Il-yong brought to the White House in 2019 when he met Donald Trump.
"I testified about Christian persecution in North Korea and I shared about my aunt's story," he said.
"I shared that even though the persecution is ongoing, people still worship there and they are craving freedom of faith."
In North Korea, December 24 is a public holiday, marking the birthday of Kim Jong-suk, the grandmother of Kim Jong-un and the first wife of Kim Il-sung - North Korea's founding dictator.
But Ju now lives in Seoul, South Korea, where Christmas Eve looks very different.
He said: "Every Christmas Eve, we gather at the church and we sing together, worship together, share meals together, and we prepare gift boxes and exchange them together."
"Normally I spend Christmas Day in the church with the church members."
He's even had the chance to experience Christmas in Britain.
He said: "The Christmas trees and neon signs were so pretty. I really enjoyed it. So beautiful."
And he's got a message for Britain this Christmas.
"When many people think about North Korea, the first pop-out image is nuclear weapons, Kim Jong-un, and famine," said Ju.
"But I really want to let people know that we need to pay attention to the people, not the regime."
Widespread flash flooding occurred on Christmas Eve in the south of the US state as a result of torrential rain.
In one mountain resort, debris and mud was filmed cascading down roads and fast-moving water was seen rushing through the porch of several homes.
The US National Weather Service said "life-threatening atmospheric river conditions" will continue throughout Christmas Day, with a rare "high risk of excessive rainfall" warning remaining in effect.
California governor Gavin Newsom declared a state of emergency in six counties to allow what he referred to as "emergency authorities and preposition resources to keep our communities safe".
An estimated 130 evacuation orders were issued to vulnerable homes, Los Angeles County officials said, many of which are in the same area that was scorched by wildfires at the beginning of the year.
Southern California typically gets up to 2.5cm of rain this time of year, but this week many areas could see 10 to 20cm, with even more in the mountains, National Weather Service meteorologist Mike Wofford said.
Heavy snow and gusts were expected to create "near white-out conditions" in parts of the Sierra Nevada and make travel "nearly impossible" through mountain passes.
There was also a "considerable" avalanche risk around Lake Tahoe, according to the Sierra Avalanche Centre.
More than 165,000 homes have had power restored after experiencing outages due to the storm, according to the provider Pacific Gas and Electric.
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California is prone to extreme weather events, not helped by the state experiencing wet periods followed rapidly by very dry weather.
The Golden State has previously suffered from drought and wildfires to earthquakes and flooding.
Sat by a Christmas tree at his Mar-a-Lago residence in Florida, the president and first lady took calls from youngsters who had dialled into the North American Aerospace Defence Command (NORAD), which tracks Santa's sleigh around the globe every Christmas Eve.
When asked by two children, aged four and 10 from Oklahoma, why Santa is being tracked, Mr Trump replied: "We want to make sure that he's not infiltrated, that we are not infiltrating into our country a bad Santa."
As Mr and Mrs Trump took about a dozen calls between them, the president frequently praised the state of the country, saying it is "in great shape" and the "numbers are great".
To an eight-year-old girl in Kansas, who said they did not want coal as a gift, Mr Trump said: "You mean clean, beautiful coal. I had to do that, I'm sorry."
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He added: "Coal is clean and beautiful. Please remember that, at all costs. But you don't want clean, beautiful coal, right?"
"No," the caller responded, saying she'd prefer a Barbie doll, clothes and sweets.
In another call, to an eight-year-old from North Carolina who asked if Santa would be mad if no one leaves cookies out for him, Mr Trump said he didn't think so, but he would be "very disappointed".
"You know, Santa's - he tends to be a little bit on the cherubic side. You know what cherubic means? A little on the heavy side," the president joked.
"I think Santa would like some cookies."
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The president appeared in a jovial mood, saying he could take calls "all day long" but quickly added that he would likely have to get back to "other things" including Ukraine, Russia and China.
At another point, while the first lady was on the phone, Mr Trump noted how little attention she was paying to him, saying: "She's able to focus totally, without listening."
He also said he loved Pennsylvania when speaking to a five-year-old boy in the state, adding that the Republicans won it in a "landslide" during the last election.
In a post on Truth Social after wrapping up the calls, Mr Trump wrote: "Merry Christmas to all, including the Radical Left Scum that is doing everything possible to destroy our country, but are failing badly."
On Christmas Eve, the White House imposed visa bans on five public figures in Europe.
It's all about what European officials describe as the regulation of online harm and what America's officials consider censorship.
"If you spend your career fomenting censorship of American speech, you're unwelcome on American soil," said Sarah Rogers, the US under secretary of state for public diplomacy, as the bans were announced.
The highest profile figure facing travel restrictions is Thierry Breton, a former EU commissioner responsible for regulating social media and a key architect of the Digital Services Act (DSA) - a piece of legislation that is very unpopular in the White House.
The Trump administration has accused the EU of placing "undue" restrictions on freedom of expression in its efforts to combat hateful speech, misinformation and disinformation.
It argues the DSA unfairly targets US companies and cities, who it is not elected to represent.
Mr Breton has already had some fiery spats with Elon Musk, the owner of X and former Trump adviser.
Earlier this year, Musk called him a "tyrant of Europe" and Mr Breton accused Musk of "lying like hell" about online restrictions he was facing.
"Is McCarthy's witch hunt back?" he posted on X after the bans were announced.
The other four people facing visa bans are from the UK and Germany and work in disinformation organisations.
They are the UK's Imran Ahmed, chief executive of the Centre for Countering Digital Hate and Clare Melford, who runs the Global Disinformation Index and Germany's Josephine Ballon and Anna-Lena von Hodenberg from HateAid.
Although this is the first time Washington has put visa bans in place, it is an argument that's been brewing for years.
Europe and the UK have much stricter controls over what you can do online compared to America.
In Europe, there is the Digital Services Act which regulates online activity. In the UK, we now have the Online Safety Act that began being fully enforced in July.
We also have a number of other laws that govern what you can say and can lead to jail time if you breach them.
Just this month, ex-footballer Joey Barton was given a six-month suspended prison sentence for "grossly offensive" posts he sent on X.
Under both of those acts, platforms hosting harmful content can be fined significant amounts, even if they're based in the US.
Musk's platform X, for example, was recently fined €120m (£104m) by the EU over issues relating to transparency.
Fines like that are what annoy the Trump administration so much. It sees rules like the Digital Services Act as governments in Europe undermining Americans' right to freedom of speech.
Ironically, that's exactly what European leaders are now accusing Washington of - overreach.
The EU commission has strongly condemned the visa bans and the UK government said it "supports the laws and institutions which are working to keep the internet free from the most harmful content".
The politician who replaced Breton in his EU commissioner role, Stephane Sejourne, said: "No sanction will silence the sovereignty of the European peoples. Total solidarity with him and all the people of Europe affected by this."