The summit in Canada was marked by Mr Trump's controversial trade policy which has put him at odds with the rest of the G7 leaders.
"There's a special place in hell for any foreign leader that engages in bad faith diplomacy with President Donald J. Trump", Navarro insisted.
Asked about Trump's tweets and the future of the G7 late Saturday during a photo op in La Malbaie, Trudeau declined to respond to several questions.
At his closing press conference, Trudeau called US steel and aluminum tariffs "insulting" and pledged to proceed with previously announced retaliatory tariffs.
Trump infuriated his G7 allies recently by slapping them with the hefty tariffs on steel and aluminum - a move that prompted Canada and the European Union to threaten duties of their own.
When Mr Trump left Quebec, it was thought that a compromise had been reached, despite the tension and the determination of European leaders Macron and Chancellor Angela Merkel of Germany to push back against the U.S. president's protectionist policies.
"He really kind of stabbed us in the back", Kudlow said.
Trump also took aim at Canadian Prime Minister Justin Trudeau and said he might double down on import tariffs by hitting the sensitive automobile industry, throwing G7 efforts to show a united front into disarray.
A proposal by United States President Donald Trump, that Russian Federation should re-join the annual gathering of the seven advanced economies of the world has caused tensions within the group, with the proposal not having been well received by the remainder of the group's leaders. And then Trudeau starts blasting him in a domestic news conference? But Trump had already said he would not hesitate to shut countries out of the U.S. market if they retaliate against his tariffs.
In an interview on Fox News Sunday, host Christ Wallace noted that Trump had ripped Trudeau on Twitter, calling him "dishonest and weak" because he gave a press conference after Trump had departed the G7 summit.
"Canadians are polite and reasonable, but we will also not be pushed around", the prime minister said.
"Kim must not see American weakness", he said.
Trump negotiated in good faith on the communique agreed by the other members of the G7, only to have Trudeau criticize US policy after he left, Kudlow said.
Canadian Prime Minister Justin Trudeau and French President Emmanuel Macron were especially vocal ahead of Trump's arrival.
"Not to sign a statement of solidarity, which stands for everything that we stand for, is a big mistake", Feinstein said.
Russian Federation was kicked out of the group in response to its 2014 annexation of Crimea.
In much of the European press, the tendency was to underscore the historical significance of the rift between the United States and its continental allies. Europe's answer must be to stick even closer together, defend its interests and strengthen alliances with countries such as Japan and Canada, he said.
A German government spokesman also said that Berlin stands by the jointly agreed G7 communique in which leaders underlined the crucial role of a rules-based global trading system and promised to fight protectionism.