I can only say that based on my experience with international trade, Canada has been ripping the US off far more shamefully than Mexico has. There is no concept of fairness in the treatment of US imports as opposed to the almost limitless access Canadian companies have to US markets. Oh, I’m sure the more politically connected US corporations bought whatever access to Canadian markets they needed, but smaller businesses have a very difficult time selling to Canada because of the duties, taxes, and regulations they retain - NAFTA notwithstanding.
Walk through the Toronto downtown financial district and look at all the American banks there...oh wait; there aren’t any. Try to buy some property in Canada as an American. See how that goes. Or try to buy mineral or timber rights. Yes, they do allow American corporations to do business there. Ford has (or had) a number of manufacturing plants in Canada (although the 351 Cleveland was a much better engine than the 351 Windsor).
Of course, I can understand why the Canadians have these restrictions. If they didn’t, we would have economically gobbled them up years ago. But the point is that an American business has far more impediments about doing business in Canada than the other way around.