EDIT: To the people downvoting this post because democrats > republicans: you’re missing the point.
“first past the post” voting always devolves to a two party system. The founding fathers knew this and warned against it. Until we get ranked choice, or something similar, we’re stuck.
Not quite.
FPTP always devolves into local two candidate elections.
There’s no guarantee, though, that those two parties are the same everywhere. Regional third parties can do quite well under FPTP. That particularly works for e.g. the Scottish National Party or the Bloc Quebecois.