So the American citizens bear no responsibility if President Biden decides to invade and occupy Canada?
Depends. For instance, when presidents like Kennedy/Johnson and Nixon said they wouldn't escalate, or would de-escalate in Vietnam, and people believed them and voted for them, then it's not the
people's fault that those guys lied through their teeth.
If it's a conflict that could not have been known (Canada), there's an election in two years, opportunity to protest, Congress can impeach him, and anyone willing to take the risk can try to take him out.
I don't know whether Putin "ran" on a invasion platform, but I don't think he's been legitimately opposed in any election. Tyrants can't be controlled by the populace and can be difficult to sack. Most people are trying to feed their families, which just became much harder thanks to Putin. I'm not going to begrudge anyone who doesn't want his family in a gulag or worse.
Perhaps some general will do the task, especially seeing how Russian troops are crying for mom and blowing up their own tanks in their "training exercise."