The transatlantic friendship that has seen Europe and the United States forge alliances on everything from defence and culture to trade and climate change since the Second World War seems to be unravelling. German Chancellor Angela Merkel said as much on Sunday, after the particularly divisive Group of Seven meeting in Taormina, Italy.

Speaking at a political rally in a Munich beer tent – she is going into her fourth election – Ms. Merkel did not mention Donald Trump by name, but it was obvious the U.S. President had triggered her comments about an emerging U.S.-Europe rift. "The times in which we can fully count on others are somewhat over, as I have experienced in the past few days," she said. "We Europeans must really take destiny into our own hands."

Brexit – Britain's exodus from the European Union – was also on her mind. "Of course, we need to have friendly relations with the U.S. and with the U.K., and with other neighbours, including Russia," she said, but added "we have to fight for our own future ourselves."

Story continues below advertisement

Read more: Trudeau and Trump talk NAFTA, global security at G7

Her comments seem to indicate she saw no improvement in her relationship with Mr. Trump after their famously frosty meeting at the White House in March. The Taormina summit turned into the G6 plus one. The event, which came to an inglorious end on Saturday, cannot be considered an outright failure. But it came pretty close.

Don't blame the Italian hosts, who had spent four solid months trying to build a consensus on key matters, such as climate change, and only partly succeeded. The exceedingly short, undetailed communiqué – only six pages long, compared with the 32-page wonder produced at last year's G7 – was evidence of the Italians' struggle to find common ground.

The main culprit was Mr. Trump, who did his best to isolate himself from the other G7 leaders – from Canada, Germany, Britain, France, Japan and Italy – on several issues pressing on the global order.

On fighting terrorism and cyberterrorism, he was in five-star-general mode, leading the charge with British Prime Minister Theresa May, who is managing the aftermath of the terrorist attack in Manchester that killed 22 people.

On trade, the G7 managed to bash out a bland statement that vows to fight protectionism but seemed to take a nod to Mr. Trump's view that the global trading rule book is stacked against U.S. interests. Shortly after the G7 communiqué was published, Gary Cohn, the White House's chief economic adviser and director of the National Economic Council, made it clear Mr. Trump would no longer tolerate trade rules that, he thinks, allow countries such as Germany to build huge trade surpluses with the United States. "We do to you what you do to us," Mr. Cohn told reporters, in effect threatening a trade war unless the United States gets its way.

But on two other big files – food security and climate change – the Americans were not part of the G7 party.

Story continues below advertisement

The Italians, who are bearing the brunt of the crisis that is sending hundreds of thousands of migrants and refugees to Italy from North Africa, had been promoting a food-security agenda, noting that more than 20 million people in South Sudan, Somalia, Yemen and northeastern Nigeria are at the risk of famine. The Italians fear mass migration and internal displacement, knowing that people who are on the verge of starvation have one of three choices – they riot, they migrate or they die.

But the G7 did not pledge to write new food-aid cheques. Had aid been endorsed by Mr. Trump, the G7 governments surely would have.

But it was the climate file where Mr. Trump broke furthest from the G7 pack. In an unprecedented move, six of the G7 leaders reaffirmed their commitment to the Paris climate-change agreement, reached in 2015 and ratified by most countries last year. The deal was considered a breakthrough after the collapse of the Copenhagen climate talks in 2009, and aims to limit global warming to 2 degrees Celsius over preindustrial levels.

Mr. Trump, who once denounced man-made climate change as a "hoax" and vowed to yank the United States out of the Paris agreement, has not done so yet. That's the good news. The bad news is he may still do so.

In a Saturday speech delivered at a U.S. military base in Sicily, just before Air Force One took off for the United States, Mr. Trump boasted about all his accomplishments in his nine-day swing through the Middle East and Europe. "Climate" did not even warrant a mention.

The other G7 leaders were close to being distraught that the Paris deal is in jeopardy. "Here we have a situation that six members, or seven if you want to add in the [European Union], stand against one," Ms. Merkel said, adding that "there are no indications whether the United States will stay in the Paris agreement or not."

Story continues below advertisement

Mr. Trump's isolation act on climate wasn't the only reason the other G7 leaders left the summit with forced smiles. The six knew months ago that Mr. Trump would be no pushover, though they probably had some hope that their combined weight could force him to bend. He didn't. Their fear, no doubt, is that future G7s and G20s will be hijacked or severely diluted by the Trumpian agenda.

Prime Minister Justin Trudeau might be their secret weapon. There is no doubt that Mr. Trudeau has been able to charm Mr. Trump, leaving the other G7 leaders astonished. The next G7 is to be held in Charlevoix, Que., and its host will be Mr. Trudeau. After the near collapse of the G7 in Sicily, Mr. Trudeau will face enormous pressure to keep the group relevant and functioning. Going up against Mr. Trump, his challenge will be formidable.