Mexico complained that the tariffs will "distort global trade" and said it will penalize US imports including pork, apples, grapes, cheeses and flat steel.
Getting the president to walk back from the line he drew in the sand Thursday won't be easy, they acknowledge.
U.S. Chamber of Commerce President Tom Donohue warned in a letter to the body's board that current trade policies could threaten economic progress and cause the loss of more than 2 million jobs, mostly in states that voted for Trump.
It is still too early to assess the economic impact of the last two days, but at some point Canada is counting on Trump's "America First" protectionism to ultimately be proven wrong.
In a CBC radio interview Friday in Halifax, Prime Minister Justin Trudeau called the tariffs "ridiculous" and predicted they would backfire.
The American exports targeted in the initial wave of European Union retaliatory tariffs are worth roughly €2.8 billion ($3.3 billion) annually, according to European Union officials.
International Monetary Fund managing director Christine Lagarde tweeted from the G7 Symposium in Whistler, Canada, that President Donald Trump's imposition of metal tariffs on key allies would disrupt trade. But he said it is unclear whether Commerece Secretary Wilbur Ross will go to China as planned for another round of trade talks.
"We can't live in a world where might makes right".
And speaking to reporters, Macron described the USA move as "a mistake in many ways because it responds to existing worldwide imbalances in the worst way - by breaking up and creating economic nationalism".
RT:To be fair to Donald Trump, he did say when he was on the campaign trail that this is the sort of stuff he was going to do. "What Canada and Mexico are willing to bring to the table is something that could deliver success".
Robert Fisher, who served under former Presidents Ronald Reagan and George H.W. Bush, and helped negotiate NAFTA, said, "I don't think it's an effective negotiating tactic, and it's an unwarranted negotiating tactic with countries that are supposed to be allies".
"The fact that the USA would impose tariffs because of that isn't that surprising", Fukaya said.
These U.S. allies are also unmistakably valuable sources of aluminum and steel for many U.S. industries.
Christine Lagarde, managing director of the Washington-based lender, also criticised Mr Trump's move in a tweet from the G7 Symposium in Whistler, Canada. The potential tariffs pack a political punch: They'd hurt constituents of House Speaker Paul Ryan, a Wisconsin Republican, and Senate Majority Leader Mitch McConnell, a Kentucky Republican.
Also, US President Donald Trump has already signaled his country would withdraw from the World Trade Organization, should it side with the European Union in its ruling.
Trump, unmoved by all of it, dug in his heels.
Trump castigated Canada in a tweet on Friday morning, saying it had treated USA farmers "very poorly for a very long period of time". "Highly restrictive on trade!" the president wrote on Twitter. Obviously the stock market agrees, because when you look what's going on with the stocks, they're starting to see I'm right, ' he said, on a day the market rebounded on a good economic report that Trump touted in advance on Twitter. All three jurisdictions are the largest trade partners of the US.
Business leaders in Canada and the US predicted dire economic consequences as result of the USA decision, which was felt widely across North America and Europe and touched off a storm of criticism on both sides of the Atlantic. "I wouldn't mind seeing a separate deal with Canada where you have one type of product. and a separate deal with Mexico".