I would actually be okay with that. I don't consider Canadians alien, and I've been arguing for union for a long time.
You seem to be assuming that democracy and human rights are what other people want. Look at the first countries we "liberated", Germany and Japan. Sure, we gave them a democratic government with human rights, but we also neutered them and subordinated them to our foreign policy for fifty years. What country would you allow to do that to us?
We did that, yes.... in response to their initiation of wars of conquest that sent half the world up in flames. How many Germans would say they were better off in 1939? I'm sure a few would, I doubt many. How many Japanese think things were better for them in 1943? Some, I'm sure... probably not very many.
At the time, of course, I'm sure almost all of them believed they were fighting for their nation, rightfully. I can hardly blame them for that. (The individual soldiers, I mean.) Can't say I would have done any differently if I'd grown up in pre-WW2 Germany or Japan... you're part of your culture and few can step outside of it an achieve true objectivity. (Many
think they can, but... that is usually pride talking, self-delusion.)
If the US government turned into some overtly oppressive tyranny, I'd probably already be fighting against it as a guerilla partisan. If someone then invaded the USA with expressed intent to depose the oppressive government and restore our own Constitution, I might well view them as allies. It would depend, to a large degree, on
who it was. China? Russia? Oh hell no. A Brit/Can/Aussie/etc-Nato alliance? Probably be okay with that, depending on circumstances.
But what if I don't
agree that my government has crossed the line into tyranny and unjustified aggression? There are some who think it already has... I think we have problems but I don't think it has risen to that level, at least not yet. If I still support my government then I will see the invaders as
invaders, and fight against them.
It's very subjective and hard to say what one will do in such circumstances, but the human
instinct is to defend home/family/community/nation against "the outsiders".