I think that gasoline is more expensive in Canada than it is in the U.S., because it is taxed at a higher rate. It's not as ridiculous as it is in Europe but it is more expensive.
And, I think there are possibly cultural reasons, Americans tend to think of their cars as an extension of their own personal image, especially here in California, and I would wager that Canadians aren't quite as materialistic. So if you drive something that's economical and slow you are a nobody, everybody who is anybody has a V8 under the hood... It wasn't until diesel pickups got fast that they became popular here.
From the Canadians I've spoken with, the fact that diesel Volkswagens and to some extent, diesel trucks, are popular there doesn't really translate over to other brands and the cars available in that country really aren't all that different from the U.S. market.
But what do I know, I've never actually been to Canada.