Trudeau didn't respond to reporters' questions when he arrived at the Chateau Frontenac in Quebec City on Sunday morning.
At a news conference to close the summit of world leaders in Canada, Mr Trudeau said the people of his country would see the United States president's line on trade as "an insult" after a long history of cooperation between the countries.
Donald Trump and the White House are going after Justin Trudeau for this G-7 remarks over US tariffs. Kudlow's remarks followed a Twitter attack on Trudeau by Trump, as well as Trump's decision to withdraw from a joint communique that he had endorsed only hours earlier.
The top White House economic adviser accused Canada's prime minister on Sunday of betraying Trump with "polarising" statements on USA trade policy that risked undermining the American leader on the eve of a historic summit with North Korea.
The statement that Trump reneged on was also signed by the heads of government of Britain, Canada, France, Germany, Italy and Japan, all of which have also been hit by the United States tariffs of 25 percent on imported steel and 10 percent on aluminum.
The PC leader who will take over as premier June 29th said "all provinces should" support Trudeau in this battle. "He is not going to permit any show of weakness on the trip".
In response to Trump's tweets on Saturday, Trudeau's office contended that the Canadian leader said nothing he had not said previously "both in public and in private conversations" with Trump.
Before the G-7 summit, Trump tussled with Macron over the tariffs.
Trump's trade adviser Peter Navarro also lashed out on Sunday at Trudeau's statements, saying they represent "bad faith".
Asked about the criticism from McCain, Kudlow said Trump had spent much of the summit advocating trade policies McCain would support.
He insists, like Trump himself has done many times, and that Canada has enormous tariffs itself - especially on certain dairy and food products. "I don't understand the obsession with trade relations with Canada", he said, given that Canada is the biggest single buyer of American goods and services in the world.