That’s no leverage. They’re not going to buying the same stuff.

It will be a lot of the same stuff. Canada's largest exports to the U.S. are energy products, forest products (lumber), and minerals and metals - all of which are also Canada's largest exports to China. One of their largest export segments to the U.S. is auto parts, because so many U.S. automakers moved their parts supply chains all over both sides of the border; that won't be replaced by China, but in Trump's trade regime it's being destroyed altogether anyway.

It won't match up perfectly, of course - but that's not the point. Canada isn't going to try to eliminate trade with the U.S., but try to reduce the degree of their bilateral trade with the U.S. They can't rely on us to honor our trade agreements or keep business practices between the two countries stable, so they have to cut down their exposure to our now-more-volatile approach to trade.

It's just strange. The administration has acted as though having freedom to operate in Greenland is of such vital strategic importance that it's worth straining NATO to the breaking point, but doesn't seem to think that maintaining good relations with Canada - who controls an area of Arctic border 10x larger than Greenland and all of our existing Northern Warning System - is worth worrying about. So we drive them to enter into stronger trade relations with China, praise them for entering into stronger trade relations with China....and then threaten them with punitive tariffs for entering into stronger trade relations with China as we wake up to what we're doing?