OK, how many hijackers entered the US via Canada?
Considering they had visas, it didn't matter which port of entry they used. They didn't carry any explosives, so please don't obfuscate the issue.
As far as muslims from Canada, how are they different from muslims in the US? If you don't want to let in muslims from Canada, who possess the legal status allowing them to do so, then aren't you building the case for re-evaluating of immigration policies, since American muslims are not different from Canadian ones? Then it would be only fair to extend new immigration policies to all and not only muslims.
Also, while Mexican border may be more secure, it's much easier to get to Mexico than to Canada.