How is this possible? First for all Canada's head of the government is the Prime minister which is the leader of the party with the most seats in the legislature instead of being a separate elected "president". What this means is that a government can be toppled early if they have the most seats but no majority in the house and the other parties decide to gang up and vote down the budget or some other "confidence" motion. This will trigger an early election.
Citizens in a riding (district for you americans) can also organize a recall referendum to force a "by-election" in that one riding/district where the sitting member has to contest for his/her seat in a special election. If the ruling party were to be forced to fight too many by-elections and lost too many seats to the opposition parties, a general election could be triggered early by a non-confidence vote.
Unfortunately, since the leader of the cabinet and the leaders in the house are separate people in the US system and because losing the majority in a house does not trigger an election, the people really have no way to topple a government they disagree with without a violent uprising.
You cannot force a reset of the house or senate through a lost vote on the budget in the US whereas in countries like Canada, if the government loses a key vote, it is considered as having lost the confidence of the people and a new election has to be called.