Why Did President Trump Place a New Tariff on Canadian Aluminum?

This is probably a Canadian aluminum worker snickering under his breath because he’s put one over on Donald Trump. But today marks an end to that.Image Source/Cultura/ZUMAPRESS

For indispensable reporting on the coronavirus crisis and more, subscribe to Mother Jones’ newsletters.It’s been just over a month since President Trump signed a new trade agreement with Canada and Mexico, so guess what he did today? He turned right around and placed new tariffs on Canadian aluminum:

The White House said certain types of aluminum were surging into the U.S., depressing the U.S. industry. The administration justified the tariffs, which will be set at 10%, using a national security provision and argued that a depressed U.S. aluminum industry threatens U.S. national security.
“Earlier today I signed a proclamation that defends American industry by reimposing aluminum tariffs on Canada,” President Trump said during a speech at a Whirlpool factory in Clyde, Ohio. “Canada was taking advantage of us, as usual,” he said. “The aluminum business was being decimated by Canada, very unfair to our jobs and our great aluminum workers.”

I don’t know about “certain types” of aluminum, but it’s pretty easy to dig up total US imports of aluminum from Canada:
Maybe I’m missing something, but it doesn’t look like there’s been a surge in aluminum imports from Canada. Maybe there is if you do it by tonnes instead of dollars? Or if you look only at certain specialized types of aluminum products? Or something.
More likely, Trump still hasn’t gotten over being humiliated by Justin Trudeau at that G7 meeting a few years ago. That’s more his style.