Mexico is a Third World country. The vast majority of illegal aliens are coming from Mexico and Central America. Canada is a developed country with a standard of living similar to ours. They have control of their borders and immigration system.
It would be dumb to construct a wall on our Northern border or to devote the same resoures to control it. In fact, Canada has more to fear from being invaded by the illegals transiting the US. We can't control our Southern border nor do we track and deport visa overstays who comprise 40% of our illegal population.
No it is not politically correct. Terrorists can cross the Canadian border also. We need to secure the borders not a border. We have lots of illegals cross the Northern border as well they just happen to not be Canadian.
Doing half the job is stupid. Close the Southern border and guess what. More people will sneak across the Northern border. No ways near as many but it will still increase and then we have to start the whole stupid fight again. Secure ALL the borders now and be done with it.