It seems I've been called out.
First, I don't know much about international stuff, except that it's a hairball and a half. Awhile back, I worked on a case involving a Canadian national sued in a US court. There was a lengthy to-do over whether he had been properly served. That was a six figure fight that lasted for over a year. He had to stay out of the US (he had business here) to keep process servers at bay. In addition to my firm, he had Canadian lawyers, and it was just a big, expensive mess.
The rules would be different if you were sued in state or federal court here, and even then, the laws are different in each state and will also vary depending on the federal circuit if you're sued in one of them instead.
If they get a judgment against you here, there are ways to register the judgment in Canada and enforce it under the Canadian system. I don't know how to do this, but it is possible. I'm not sure how Canada handles that. Canada inherited the common law system from the UK, which is similar to the US (and well-run), so I'm sure there's some sort of due process and certification of the judgment, certain procedures required for collecting the judgment, and so on.
Also, there might be a process for the company to file suit against you in Canada, too. I'm not sure, but they most likely allow foreign companies to have jurisdiction if they do business in Canada or submit to jurisdiction. The US (usually) allows that and my gut says Canada would be similar.
So... I can't give that good of an answer here. There are lots and lots of variables. Even if you're in the right, you can get stuck with some hefty legal bills. International law can be expensive.
