A lot of people just misunderstand the conflict.
The things we sell the US are the raw components that go into all of the value add products they make. Oil, aluminum, potash, rare earths, etc. Without those things their economy doesn't function. The things they sell us are access to intellectual property, online services, value added products (car parts, etc) that they made out of the raw materials we sold them, etc.
Many of the things we sell them have no obvious competition, not at the prices the US is used to enjoying. Can they buy potash from Belarus? Sure, but the transportation is going to cost as much or more than the Potash, doubling prices. There are competing products for the things the US sell us. The Canadian government could easily cancel every license of windows and switch to Linux (as France and a few other euro gov's are in the process of right now) and not only never miss a beat, but cut a line item off of the budget at the same time. Both are exports, but one is essential and one just isn't. That's the nature of our economic relationship with the US. We give them a bunch of essential raw components that make their economy go, and they sell us back value added stuff that almost entirely non essential.
This doesn't mean that they can't hurt us, but to really do it they would have to endure economic hardship that the American public just isn't ready for.