To have a real winner the president needs 270 voices in the electoral college, if a third party won enough States that wouldn’t happen, what then?

Same in the Senate and Congress, if neither the Democrats or the Republicans have enough seats to have a majority because of a third party, they’ll need to work with that party.

Just because it’s not part of the culture it doesn’t mean it can’t happen and that politicians won’t have to deal with it if it does.