A country doesn't get attacked and invaded to change basically nothing or increase the life of the foreign population. It's done to exercise sustained power.
Who do you think would Canadians vote for after Trump starts a war, kills hundreds or more Canadians, etc.? So, for sure they wouldn't get voting rights, for example.
You have a way too romantic idea in your head. "We attack and kill our friends to become better friends" isn't a real thing.
> Or when they get access to Hulu and to the US Netflix catalog. Etc., etc.
Or when they can't afford health care anymore. Or when employees lose rights. Or when the country gets flooded with fire arms. You might think becoming part of the US is the totally best that could happen to anybody and that's okay. But most people outside the US don't agree.