I never said Canadian students aren't counted in the international category. However, that being said, I don't think all international students are considered equal. In pursuing their goal of assembling a diverse class, law schools probably want variety in their international applicants. If a school takes 20 international students out of a pool of 50 canadians, 10 brits, 15 people from asia and 5 from africa, then--all else being equal--you probably have a lower chance to get in as a Canadian applicant than if you are a British applicant.
As far as a US resident with an undergrad at a Canadian university, you're probably going to be in the same pool as other US residents. You'll also probably be at a slight disadvantage since Admissions officers probably know less about the quality of your undergraduate university.
I think the more interesting question is whether it helps or hurts your chances to be an international applicant in general. I think this one entirely depends on how many international students each school aims for each year, and the ratio of international to US applicants it recieves. Since I don't think that kind of data is published anywhere, we're pretty much left guessing. If you want an informal idea, try looking at LSN and figuring out the average numbers for US and International applicants admitted at the university you're interested in last year.