Why are third$-$party candidates more successful in other democratic nations compared to the United States?

Other democratic nations are less hyperpartisan and therefore more accepting of other parties, while hyperpartisanship in the United States creates a strict two$-$party system.

The United States has passed laws that prohibit third$-$party candidates from holding positions in the federal government, unlike other democratic nations.

Many democratic nations have set quotas for how many members of each party must be present in the government, unlike in the United States.

Other nations have a proportional representation system, while the United States uses a single member, first past the post system of representation.