Mr Trump's strained relationship with the rest of the G7 was in evidence on Saturday when he arrived late for the opening session, with Mr Trudeau addressing a gathering that included an empty chair where the president was meant to be.
He blamed past world leaders, including past presidents, for that situation, but said the current crew - including Prime Minister Justin Trudeau - now know that the "gig is up".
Trump's fellow G7 leaders watched him as he slowly made his way to his seat, which was across from Trudeau and next to International Monetary Fund managing director Christine Lagarde. "I don't understand the obsession with trade relations with Canada", he said, given that Canada is the biggest single buyer of American goods and services in the world.
On Sunday, Trudeau the younger demurred even more, choosing instead to send out messages of his own about democracy, women's empowerment and the environment.
Heading into the leaders' summit in La Malbaie, Que., there were deep concerns the G7 alliance was fast becoming a G6 plus one because of a widening gulf between the USA and the rest of the group in key areas such as climate and trade.
At the end of a long weekend of rhetorical salvos over the G7 summit's chaotic ending, German Chancellor Angela Merkel added her voice to the chorus, saying she found Donald Trump's actions "sobering and a bit depressing", while calling for more civility in global exchanges.
Prime Minister Justin Trudeau, British Prime Minister Theresa May, French President Emmanuel Macron, German Chancellor Angela Merkel, Japanese Prime Minister Shinzo Abe and U.S. President Donald Trump discuss the joint communique following a breakfast meeting on the second day of the G7 meeting in La Malbaie, Que., on June 9, 2018.
Trump's closest advisers added to the attack during televised interviews on Sunday.
As he exited the world summit, Trump had delivered a stark warning to America's trading partners not to counter his decision to impose tariffs on steel and aluminum imports.
Kudlow accused Trudeau of "pouring collateral damage on this whole Korean trip".
"I highlighted directly to the president that Canadians did not take it lightly, the United States' move forward with significant tariffs on our steel and aluminum industry", began Trudeau. Trudeau made an error.
Vice President Mike Pence told Trudeau he would have to agree to that before Trump would agree to meet him. Despite his sharp differences with US allies, the president insisted he has a "great relationship" with his foreign counterparts.
The prime minister responded by remaining above the fray.
Ten minutes later, the French President's office released a photo that shows Mr Macron negotiating with his American counterpart, gesticulating to make a point.