I would guess too that it's far easier for the average Canadian to adjust and assimilate into the US and it's culture than it would be for the average US citizen to adjust and assimilate into Canada's culture.
Take basically every major Canadian city, Edmonton excluded, and drive two hours south. Where are you at?...somewhere in the US. The vast majority of Canadians live and work fairly close to the US and are much more exposed to US culture through radio, TV, tourism and other experiences.
That sort of familiarity with Canada isn't the case in the most US. Seattle, Detroit and Buffalo are close enough to be subject to Canadian influence...but that's about it as far as major US urban areas go. Most US people live far enough away from Canada to have little or no real experience with Canada or Canadians.
As a whole, Canada is just far stranger to the US than the US is to Canada.