Could Europe, China, Mexico, and Canada halt all trade with the US to force Trump out?

Sure they could, if they could agree long enough, but if you're asking coukd they force Trump to step aside, I very much doubt it.

Besides, if it's wrong for Russia to meddle in our elections, how could it be right for other nations to influence our governance?

It would significantly stress the US economy, and their own.

Not without damaging themselves

Americans would have to vote him out.

Theoretically yes but in real terms extremely unlikely as it would not only hurt the American economy but also their own.

That would create dire situations worldwide.

Unfortunately that won't happen.