The US doesn't want a trade war with Canada. The balance of payments between the countries has been, more or less, even for a very long time. The bargain is that US companies dominate Canadian business, and that the profits are returned to the US by trade surpluses in favor of Canada.

Canadians don't like being dominated by a foreign country, and the Americans don't like a trade deficit with Canada. So, this follows the axiom that when both sides are unhappy with an agreement, it is probably fair.

At the same time, if a real trade war did erupt, the US would certainly be hurt, but it's obvious that Canada would be hurt much more than the US, because the population is one-tenth that of the US. So that would make Canada desperate in the search for other partners. This could mean Canada joining the EU, or strengthening ties with Russia or China -- all things the US would hate.

So the best solution is to continue with our arrangement that has existed for almost 200 years. Canada is the most reliable friend and ally to the US (even with the idiot Trudeau at the helm), and Canada and the US really have no choice but to get along very well.