As a happy, patriotic Canadian with nothing but love for my country and a deep understanding of the differing cultures and subtle differences in everyday life from city to city, I say this is a rather terrible idea. There's a lot to be seen post-apocalyptic in Canada, sure, but there's more in places like the UK, Japan, Africa... just about anywhere.
In order to have enough of a difference in tone, characters and setting, it couldn't take place during the 1950s... Canada was in a place then that couldn't be well-shown or exaggerated the way it would need to, to make a full-scale Fallout game. It would have to take place earlier. I'd like to see more games take place in Canada (or anywhere other than Africa, the middle east and the U.S.), but Fallout isn't one of them.