Like Trump says that the cartels have invaded Canada wouldn't they have to pass through the US, avoid checkpoint, border control on both sides and many other things? So Canada can only blame the US?
I'm not gonna touch the insane ramblings of the Cheeto, but I will remind you that the oceans exist and you can very easily take a boat from Mexico to Canada without ever entering the US if you wanted to.
Avoid populated areas, and fly low. The exact same techniques that they've been using for decades. Radar is dumb, it sends back a return when it bounces off objects, but you can't tell what it is returning, that's why planes have transponders to supplement more info. If you just don't do that and fly low it will get filtered out with the terrain most of the time.
Couldn't they also just legally request a route and land on an official airport (no matter the exact size) with a few people on board as a sort of "VIP" flight and then just smuggle the drugs out of the plane/airport?
It wouldn't be the first nor last time someone in a harbor or airport was bribed to "misplace" some cargo they handled/saw/whatever.
This highlights the folly of trying to lock down the Canada-US land border. If you really wanted to cut down drugs and human trafficking, you'd focus on ports of entry to the continent. The border is just way too long. Only an idiot would try to police its full length. If you think it's only the 4000 miles from Maine to Washington State, you're forgetting that extra 1500 miles with Alaska.