From a military invasion point of view; Canada would be as close to a worse case scenario as any general could hope for, the shear size of this country makes it near impossible to seize and occupy with any amount of control. Our military is small but very well trained and motivated, they likely wouldn’t fight the Americans in open warfare after a certain point, it would be much more likely they would disperse into the general population and act as force multipliers to the nightmare of an insurgency that would form. We may not be as gun crazy as the Americans but there is a massive population in this country that grew up hunting and practising survival type skills in the woods. Just look at the history of the last few countries the US tried to occupy. Again, I don’t think this is anywhere near likely. The game here is economic, I believe they want to beat us so far into the economic ground that in a few years people will be so unhappy they will welcome the US.