Given that both Canada and Mexico account for significant amounts of the steel we import (while China supplies only about 2% of imported steel), and Canada provides us with something like half our imported aluminum, and also given that Congress has shown no great signs of agreeing with Trump that NAFTA is “the worst deal in history” or of wanting to back out of it, you have to wonder if this tariff stunt is just Trump’s braindead attempt to blow up NAFTA on his own.