Verified answer

Because Yahoo Canada still uses the American dictionary. Crazy, isn't it?

Yes, it knows that you're likely located in Canada due to a form of reverse IP look up. Online advertisers use such in order to have targeted ads come up to increase likely buying. It would be inappropriate and irrelevant to provide Canadian "heart"ers with ads about say Greenland. Or maybe yahoo just wants to keep ya happy. They've been known to do that.