Kudlow had been negotiating nicely with Trudeau at the summit in Quebec and the U.S. had agreed to join the joint communique, but Trump pulled out after he felt betrayed by Trudeau's news conference where the prime minister called Trump's tariffs on Canadian aluminum and steel exports "insulting".
Guy Verhofstadt, a former Belgian prime minister who as an MEP now co-ordinates Brexit talks for the European Parliament, mocked Mr Trump's temper and supposed closeness to Russian President Vladimir Putin in a series of tweets.
The President upped the ante in a Twitter barrage aimed at Mr. Trudeau after the summit, threatening "Tariffs on automobiles flooding the U.S. Market!" "Why should I, as president of the United State, allow countries to continue to make massive trade surpluses, as they have for decades, while our farmers, workers & taxpayers have such a big and unfair price to pay?"
He injected additional controversy by suggesting that the G7 offer a seat at the table to Russian Federation, which was ousted from the group after it annexed Crimea.
White House economic adviser Larry Kudlow continued the war of words between the Trump administration and Canadian Prime Minister Justin Trudeau on Sunday morning. She also described her impression from Trump's behavior at the summit as "disillusionment". Gallup has Trump at 41 per cent approval and 55 per cent disapproval.
Still, the fundamental differences remained clear.
Trump also criticized former President Barack Obama because he "allowed" Russian Federation to annex Crimea.
Mr Trump said the USA paid "close to the entire cost of Nato" to help protect countries that "rip us off on trade".
Both sides suggested some progress in NAFTA talks.
British Prime Minister Theresa May "is fully supportive" of Trudeau and his leadership, a senior United Kingdom government source said, while European Council President Donald Tusk tweeted: "There is a special place in heaven for @JustinTrudeau". "But it did not start with this G7, but with the election of Donald Trump", said a European official. But lo, by the time I landed in Hong Kong to change flights I read that there was a joint communique.
Trump's relations with the others have hit such a low point that a key question was whether the seven countries can agree on a joint statement of priorities at the conclusion of the meeting.
The Prime Minister's Office did release a statement late Saturday, following Trump's tweets that said: "We are focused on everything we accomplished here at the G7 summit".
Before arriving at the Quebec summit, Trump injected fresh drama by asking why Russian Federation wasn't included in the group. "They should let Russian Federation come back in because we should have Russian Federation at the negotiating table".
Russian Federation was pushed out of what was then the G8 after it annexed Crimea from Ukraine in 2014.
Mr Trump's salvo capped a rollecoaster two days of controversies that began with his suggestion Russian Federation be readmitted to the G7, then what a French official described as a "rant" full of "recriminations" against U.S. trading partners, followed by a denial of any tensions with leaders at the summit and his description of their relationship as a "10".