Hours after Mr Trump withdrew his support for the joint statement and attacked Mr Trudeau, Mr Kudlow and trade adviser Peter Navarro drove the message home on Sunday morning news shows in an extraordinary assault on a close United States ally and neighbour. He complained that he had been blindsided by Canadian Prime Minister Justin Trudeau's criticism of his tariff threats at a summit-ending news conference.
Trump's actions are being called ludicrous and absurd - but then again, coming from a man whose only experience before entering politics was as a businessman (with highly questionable dealings and tactics) and a reality TV show host, might not be all that surprising. "Canada, thank you for the flawless organisation of G7", Tusk tweeted.
"He really kind of stabbed us in the back", Kudlow said.
Trump fired off a volley of tweets on Monday further venting anger at North Atlantic Treaty Organisation allies, the European Union and Trudeau.
"The U.S. pays close to the entire cost of NATO-protecting many of these same countries that rip us off on Trade (they pay only a fraction of the cost-and laugh!)", Trump tweeted.
Even Hollywood actor Robert de Niro was weighing in.
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"Very dishonest and weak".
And on Twitter, the hashtag #ThanksCanada was trending with Americans thanking their neighbours to the north for everything from Nanaimo bars to hockey to caring for airline passengers during 9/11.
According to Trump, it's not fair that other countries like Canada and India "have trade barriers against our farmers". "I don't understand the obsession with trade relations with Canada", he said on Fox News, given that Canada is the biggest single buyer of American goods and services in the world.
The former Conservative prime minister said that while he believes the dispute is serious, that doesn't make it "lethal".
About that meeting, Trump said "within the first minute, I'll know" whether the North Korean leader wants to negotiate seriously with the US.
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Trump has dangled the prospect of economic investment in the North as a sweetener for giving up its nuclear weapons. The broad agreement was light on specifics, largely reiterating previous public statements and past commitments.
As the negotiations carried on, House Speaker Paul Ryan has already warned that the time for reaching agreement that could clear U.S. Congress already passed. Lindsey Graham, R-S.C., also called Trudeau's comments a stab in the back to Trump.
British Prime Minister Theresa May offered some support for Canadian Prime Minister Justin Trudeau in the fallout from the Group of Seven leaders meeting in Quebec, but she stopped short of condemning critical comments made by U.S. President Donald Trump's trade adviser.
Trump took to Twitter late on Thursday as well to respond to the leaders of Canada and France.
The summit was seen as an opportunity to overcome disagreements on new tariffs imposed by the U.S. on imports.
Adding to the uncertainty is European anger over Trump's decision to pull the United States out of the worldwide nuclear agreement with Iran.
He said: "International co-operation can not depend on being angry and on sound bites".
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Staffers who have left or been forced out of their jobs have described a dysfunctional and toxic working environment. The White House Office of Communications has been one of the most volatile of the Trump administration.
We have very little use for Trudeau, that avatar of chic progressivism, or for Trump's other foil, Angela Merkel, the very embodiment of the short-sighted and high-handed European establishment.