The modern US hasn’t fought a war with someone right next door, who looks and talks like them. Not only would it be hard to hold captured cities, but I think many Canadian fighters would walk across that massive unsecured border and start fucking up US resources like electrical stations, water supplies, subway systems, internet backbones, government buildings, . It is super easy to buy guns and ammo in the US, bombs are not hard to make. We would have a fair amount of local support as well.

We Canadians could just walk around the US in public and you’ve never know it.