I've never heard that anywhere. Gut feelings are good only to assess whether you've got intestinal parasites. Canadian students are international; just pick up any brochure that describes class composition. Several will give you the country of origin of their international students. Canada is invariably there.
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.
Yes, if you went to U of T or McGill, you're probably good. Not quite as good as you'd be had you gone to an Ivy League, but it certainly won't count against you.On the other hand, there's plenty of good universities in Canada that have almost no international recognition at all.