As an American who now lives in Vancouver, I can say that yes, I do believe that many Canadians have very strong accents. You can't discount the "aboot" factor, because I do hear it quite a bit. But there is an inflection in the way many Canadians speak that you don't hear south of the border. There is also the differences in pronunciation that Cockroach alludes to, mostly in the "a," "e," and "o" sounds in words like "pasta," "process," and "Ikea" for example.

It's kind of a hybrid of a "Fargo" accent mixed with British pronunciations...

Of course, I'm not savvy enough to know the regional Canadian differences yet (though some of my co-workers from Nova Scotia have vaguely British accents).