I think you’re right that Canadians and Mexicans know this and still want to be friends, but it doesn’t matter. The United States has officially and democratically become hostile to them, and they’re going to have to change the way they think about the relationship. An America that can’t be trusted reliably simply can’t be trusted.

Edit: But this doesn’t mean further conflict is inevitable! The sane citizens of each country will just need to work around the problem.

I don’t think they feel betrayed by Trump, but rather the United States. One of their closest friends just declared economic war on them for no reason. The shattering of trust isn’t less painful because they had advanced notice.