you'd better hustle and get Trump elected so there can be a wall between Canada and the US
I can't see why a wall would be necessary.
Simple landmines all along the (north side of the) border should be sufficient. It would cost more than the mines, but I guess you could bolster it up with drones flying the border 24/7 and gunning down anyone coming from the north. That might be a little better, all things considered.