Toronto, British Columbia, and Waterloo are considered to be the strongest math programs in Canada. Some would also include McGill and Alberta in this list. These universities are all very competitive and have much higher expectations than most American schools (at least in terms of undergraduate coursework). Classes in Lebesgue integration at Toronto and McGill, for instance, are offered as a third year course and cannot be taken for credit counting towards a graduate program.
A difference to note between Canadian and American schools is that Canadian schools require a masters degree before entrance into a PhD program. However, masters programs are fully supported in Canada.