That's yet another variable. I would think, though, that Canadians would be quite similar to us in terms of overall health, nutrition, etc. Our lack of SARS deaths here in the US could just be a temporary anomaly that will, sadly, be "corrected" all too soon. We just don't know enough now.
The place where I'm most worried about SARS gaining a foothold is North Korea. With virtually no health care system and so many North Koreans on the brink of starvation, it could wipe out a huge percentage of the population there, and the ensuing panic and flood of refugees could very well destabilize the entire region.