The tariffs, as well as Trump's noted opposition to multilateralism, his criticism of Canadian trade barriers and suggestion that the union become the G8 with the inclusion of Russian Federation made for a chaotic lead into the G7 summit.
"This isn't just G7. I mean seriously, Russia, who took over Crimea, all the violence that's taken place in Ukraine, the poisoning of people in the United Kingdom, the influence in our election this last time period", Heyman recounted. And we charge nothing. He threatened to stop all trade with any country that did not lower or even eliminate tariffs.
According to the USA trade representative, however, there was an $8.4 billion U.S. trade surplus with Canada on goods and services in 2017.
"If they retaliate, they're making a mistake", Trump said.
In London, Mayor Sadiq Khan said he hoped Trump would reconsider policies such as the recent increase in tariffs on steel and aluminum from Europe, China, Mexico, Canada and elsewhere.
Commentators saw a parallel in past tensions between Trudeau's father and Richard Nixon, when the then-leader of the United States called Trudeau senior, in private conversations, a "pompous egghead" and a "clever son of a bitch".
The moment he left for the airport on Sunday, he let the tweets rip his host.
U.S. President Donald Trump's tweet storm after the G7 summit prompted support for Prime Minister Justin Trudeau from some prominent conservatives.
Describing the U.S. tariffs on European steel and aluminium as "unjustified", she left no doubt that EU nations would impose counter-measures on USA goods in response but cautioned against tit-for-tat retaliation which might lead to a trade war.
On Twitter he accused Trudeau of "false statements" and wrote that he had ordered his aides to withdraw US endorsement of the joint communique.
Mr Trump said the move was based on Mr Trudeau's "false statements. and the fact that Canada is charging massive tariffs to our U.S. farmers, workers and companies".
Still, other Trump advisers had taken up the attack in appearances on Sunday's news shows, leveling more withering and unprecedented criticism against Trudeau, branding him a back-stabber unworthy of Trump's time.
His aides took the matter further.
"He really kind of stabbed us in the back", Kudlow said on CNN. I do not know where we go from here.
He tweeted that the Canadian PM was "dishonest and weak" and directed his envoys not to agree to the final communique that normally is released at the end of these multilateral meetings. "We joined the communique in good faith", Kudlow said.
Trump has been on a tear about German trade and cars in particular, bringing up the issues with other European leaders with whom he has met over the last few months, the source said.
Navarro, the Trump trade adviser, said his harsh assessment of what "bad faith" Trudeau did with "that stunt press conference" on Saturday "comes right from Air Force One".
But California Sen. Dianne Feinstein, a Democrat, said Trump wasn't just taking on Trudeau, but all of the United States' best allies by not signing the G-7 statement after a two-day meeting in Canada with leaders of the world's largest industrialized economies.
Trump was quiet after touching down in Singapore on Sunday night but was back online first thing Monday morning, engaging Trudeau again in a war of words.
"I've never seen language like this, least of all from subordinates of the president directed at the prime minister of their greatest friend and ally", Mulroney said.
He also got direct personal support from some European leaders.
Trump and his surrogates have trumpeted the myth that we have a trade deficit with Canada.
Liberal MP and former dairy farmer Wayne Easter said there was a real sense of panic building in his P.E.I. riding over the implications of Trump's pronouncements following his departure from the G7 gathering.