Not the case now, I'm sure...phones purchased outside of N. America will work (and have worked) fine with N. American SIM cards. And it's been my experience that just because a network claims to not support it doesn't mean it won't work outright. Yes, some features need to be enabled at the main server, but others just work.
OOC: I'd think that AmeriCanada would only serve to anger the person you label as such, since they may not wish to be affiliated with the other country. Though that may not be the case with some Americans...I hear they sell kits down there now to travellers to teach them how to be Canadian xD
Just stick with North Americans...safer.