[FredPret]

For any armed force, even a 2-3 million strong one, fighting a war against an entire population of 40 million goes one of two ways:

- unimaginable atrocities that would make Hitler blush, and then they might still lose

- Vietnam x 100

[machomaster]

How many of those 40 millions have military education/skills, are willing to use them, as well as have access to weapons?

[FredPret]

I don't know, but let's do a thought experiment.

North Vietnam had 13 mil people, South Vietnam 17m. Afghanistan had 20m people at the time of invasion.

These were undeveloped countries with very low human capital. Their militaries did not hold up. And yet - how did it all turn out for the US?

Canada has 40m people, terrain ideally suited to guerilla warfare, a huge land border with the US, and a population that is not only indistinguishable from American civilians, but also enjoys much wider popular support in the US than the Vietnamese ever did.

It would be extremely foolish to think you could simply invade such a place at all, nevermind easily.