The summit in Canada was marked by Mr Trump's controversial trade policy which has put him at odds with the rest of the G7 leaders.
"POTUS is not going to let a Canadian prime minister push him around", he said. He really, actually, you know: "he did a great disservice to the whole G-7", he said.
"That's what weak dishonest Justin Trudeau did", he added.
Mr Trump's presidency has been clouded by a federal investigation into alleged Russian meddling in the 2016 presidential election, and possible collusion by his campaign.
"In the name of the Western allies, he ought to come out today and wish President Trump well in the negotiations, instead of taking potshots at us", Kudlow said.
At the summit, of which the build-up to had been dominated by Mr Trump's decision to slap tariffs on steel and aluminium imports, the world leaders had agreed a statement that read: "We acknowledge that free, fair and mutually beneficial trade and investment, while creating reciprocal benefits, are key engines for growth and job creation".
On 31 May, the Trump administration confirmed that it would be going ahead with imposing additional tariffs on steel and aluminium imports from Canada, Mexico and the European Union, with trump tweeting about rectifying "unfair Trade Deals with the G-7 countries" hours before the summit.
Mr. Trudeau's office responded to Mr. Trump's tweets accusing the Canadian leader of "false statements" on Saturday, saying that the Prime Minister said nothing during the G7 summit that he had not said previously.
"I have instructed our U.S. Reps not to endorse the Communique as we look at Tariffs on automobiles flooding the U.S. Market!", Trump tweeted Saturday evening while en route to Singapore aboard Air Force One.
Trump planned to leave the summit on Saturday before it discussed climate change and the health of oceans, underlining fractures in the G7 exacerbated by US trade tariffs.
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She has since been fired and a review of her applications was initiated, resulting in at least 291 revocations. The state of Florida gave out concealed weapons licenses to almost 300 people who never should've gotten them.
Trump's change of heart appeared to have been invoked by Trudeau's comments on Trump's steel and aluminum tariffs against Canada and other allies.
The EU then announced tariffs on U.S. goods ranging from Harley-Davidson motorcycles to bourbon.
It was an unprecedented attack on the leader of the United States neighbour and ally.
"Canadians, we're polite, we're reasonable, but we also will not be pushed around".
Sen. Dianne Feinstein (D-Calif.) said it was wrong for Trump to pull out of the joint G7 communique that would have showed solidarity with America's best allies.
In response, Canada, Mexico and the European Union said they were putting in place their own retaliatory measures.
The G7 also endorsed Britain's accusation that Moscow was behind the poisoning attack in England on former double agent Sergei Skripal and his daughter - but Putin said they had "again" failed to provide evidence that Russian Federation was behind the attack.
He was reacting to Trudeau's declaration that Canadians would "not be pushed around" and would hit back at punishing USA tariffs on metal imports with "equivalent tariffs".
"I would say the relationship is a 10, and I don't blame them".
A German government spokesman also said that Berlin stands by the jointly agreed G7 communique in which leaders underlined the crucial role of a rules-based global trading system and promised to fight protectionism.
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