Trudeau "kind of stabbed us in the back", Kudlow said.
The announcement and Trump's planned tariffs have also put him on a collision course with Trudeau, leader of another key United States ally. "He did a great disservice to the whole G-7".
Mr Trump had already threatened to divide the G7, made up of the US, France, UK, Italy, Germany, Japan and Canada, when he suggested Russian Federation should be allowed to rejoin the group.
Trudeau's office responded to Trump's tweets with a written statement, saying the prime minister's comments in public and in private with Trump were "nothing he hasn't said before" and that he was "focused on everything we accomplished here at the G-7 summit".
"I have made it clear to [President Trump] that it is not something we relish doing, but it is something that we absolutely will do", Trudeau said.
"Canadians, we're polite, we're reasonable, but we also will not be pushed around", Trudeau said at the G7.
The President's characterization of the United States' relationships with allies as "a 10" when asked at the news conference about any tensions between his administration and other G7 nations also drew criticism from a senior European diplomat.
The EU then announced tariffs on USA goods ranging from Harley-Davidson motorcycles to bourbon.
The outburst against Trudeau, and by association the other G7 members, is only the latest incident in which Trump has clashed with the US' closest allies, even as he has had warm words for autocrats like Kim and Russian President Vladimir Putin. "Our tariffs are in response to his 270 percent on dairy".
The former Federal Bureau of Investigation director says Canada is crucial for national security.
W.H. trade adviser Peter Navarro: "There's a special place in hell for any foreign leader that engages in bad faith diplomacy with Pres. Donald J. Trump and then tries to stab him in the back on the way out. that's what bad faith Justin Trudeau did".
"Very dishonest & weak", Trump said, adding that recently imposed USA tariffs on imports of Canadian steel and aluminium were in response to similar measures imposed on American dairy products by Canada.
Larry Kudlow said Mr. Trump negotiated in good faith with fellow global powers in Quebec.
Trudeau later said he reiterated to Trump that tariffs will harm industries and workers on both sides of the U.S.
"You can't make this stuff up", Sachs concluded.
"That's what weak dishonest Justin Trudeau did", he added.
The Prime Minister said she had used the event as a chance to register the UK's "deep disappointment" with President Trump's plans.
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.
As Trump proceeded to take his seat, photojournalists captured one of the most iconic moments of the G7 Summit - a not-too-impressed Lagarde looking disapprovingly at the US President.
A German government spokesman said Sunday that despite Trump's retraction, Berlin stands by the jointly agreed G7 communique.