Appearing on separate news shows, Kudlow accused Trudeau of "betrayal" and Navarro called the news conference a "stunt" and went on to assail the prime minister in unusually harsh terms.
"I own that, that was my mistake, those were my words", he said.
Mr Trump's advisers said the U.S. president believed he had been stabbed in the back by Mr Trudeau over USA tariffs.
Trump also called Trudeau "very weak and dishonest" following the summit.
Navarro's comments were part of the White House's continued criticism of Trudeau..
Navarro's willingness to walk back his outburst marked a departure from the Trump administration's never-say-you're-sorry approach to political crises.
The president's staff then blasted Trudeau on Sunday with economic advisor Larry Kudlow accusing Canada of stabbing the U.S.in the back. U.S. President Trump and North Korean leader Kim Jong-un held the historic meeting between leaders of both countries on Tuesday morning in Singapore, carrying hopes to end decades of hostility and the threat of North Korea's nuclear programme.
Chrystia Freeland, Canada's Foreign Affairs Minister, told reporters in Quebec on Sunday: "Canada does not believe that ad-hominem attacks are a particularly appropriate or useful way to conduct our relations with other countries".
Trudeau, who had said at the news conference that Canada would retaliate for new USA tariffs, didn't respond to questions about Trump when the prime minister arrived at a Quebec City hotel Sunday for meetings with other world leaders. "That's going to cost him a lot of money".
It came sandwiched between tweets railing against Canada, Germany, and the European Union over their "unfair" trade with the USA, and accused them of taking advantage of American workers. He also said the USA had a trade deficit of $17 billion with Canada, though he implied that it might be as large as $100 billion.
Trump and Navarro in ratcheting up tensions with Canada since the tariffs were announced at the end of May. "Canada does have very big advantages on us in terms of trade deficits".
The Office of the United States Trade Representative's notes that the United States had an $8.4 billion trade surplus with Canada in 2017.
Asked if these were statements from the President, Navarro said they were his words, but that they reflected "the sentiment that was on Air Force One".