Kudlow, who was in Canada with President Trump for the G-7 meeting, told CNN on Sunday that the USA had come to an agreement with the other highly-industrialized nations in the group on a joint communique until Trudeau's "sophomoric play".
Trudeau also said Canada would move forward with retaliatory measures on July 1 in response to tariffs on steel and aluminium imports into the U.S. from Canada, Mexico and European Union (EU) countries announced by Trump on May 31.
Bashing the leader of one of America's venerable allies, the White House escalated its trade tirade and leveled more withering and unprecedented criticism Sunday against Canada's prime minister, branding Justin Trudeau a back-stabber unworthy of President Trump's time.
Members of Trump's inner circle continued the attacks, with both chief economic adviser Larry Kudlow - who said that Trudeau had "stabbed us in the back" - and Peter Navarro, Trump's trade adviser, directing a series of stinging comments at the Canadian leader.
"Fair Trade is now to be called Fool Trade if it is not Reciprocal", Trump tweeted, as he criticized Canadian tariffs on imports of United States milk.
Trump was referring to Prime Minister Justin Trudeau in the tweet.
In a news conference after the summit, Trudeau reasserted his opposition to the USA tariffs and vowed to press ahead with retaliatory moves on 1 July. "That's what weak, dishonest Justin Trudeau did". A senior USA administration official said that Trump had been angered by Trudeau's comments.
"In a matter of seconds, you can destroy trust with 280 Twitter characters", German Foreign Minister Heiko Maas said when asked about Trump's decision. She said in contrast she preferred to see situations as "win-win".
"The president will continue to say what he says", he said of Trump.
More broadly, Trump officials have repeatedly said that the US has the lowest trade barriers in the world to bolster their argument for imposing tariffs on other countries. He justified President Trump's decision to drop out of a joint statement made by G7 countries this weekend. I mean, we have India, where some of the tariffs are 100 per cent.
"[Trudeau] really kind of stabbed us in the back", Kudlow said.
"Canada does not conduct its diplomacy through ad hominem attacks ... and we refrain particularly from ad hominem attacks when it comes to a close ally", Canadian foreign minister Chrystia Freeland told reporters on Sunday.
"Fair trade is now to be called fool trade if it is not reciprocal", he wrote in another, referring to Canada's allegedly unfair trading policy with the USA and continuing his personal twitter feud with Canadian Prime Minister Justin Trudeau. At one point he wrote, "Justin acts hurt when called out!" Canada is the top U.S. export market, with the country buying more than $340 billion in American goods and services in 2017, according to data from the U.S. Trade Representative.
Then, he went on about how massive trade surpluses were not fair to the American people and how the United States pays almost the full cost of North Atlantic Treaty Organisation which protects "many of these same countries that rip us off on Trade" and remarked, "Change is coming".
"We commit to modernize the WTO to make it more fair as soon as possible".
"Not fair to the PEOPLE of America!"
On June 1, Trump sends the first of several Twitter salvos against what he says are Canada's unfair trade policies - "Canada has treated our Agricultural business and Farmers very poorly for a very long period of time".