EDIT: I am indeed wrong! A non-Canadian company could hypothetically get in trouble for violating these rules. I wouldn't expect that to happen often.
Also, thankfully, the Canadian rules seem pretty reasonable. Everyone probably should have to get explicit (more than a prechecked box) permission before adding you to a mailing list.
(Sorry for being harsh, but we need to get the correct message out there).
Source: hours spent with our lawyers going over this.
There is big liability here for US companies sending email into Canada (or Canadian firms sending to Canadians).
Of course it can. If they do business in Canada or maintain any assets their those transactions can be blocked or the assets frozen. Many developed countries have reciprocal agreements on things like court judgments, asset seizure and so forth. It's not the same as for a firm based in Canada, but it's not toothless either.