The problem with the US Congress isn't the two party system. The two parties are simply a reflection of the fact that this country has two sides, and each side is irreconcilable with other. They literally hate each others' guts, to the point where the political minority in a given state is now moving to states that share their politics, hardening the red state/blue state divide, a process political scientists call "The Great Sort". You could eliminate parties altogether and mandate that elections are no -partisan and we'll still have the same problems. Eliminating first-past-the-post and implementing ranked choice this or that wouldn't change a damn thing as long as there are two Americas that loathe each other so much.