The system in the US is such that only two national parties can exist with any kind of stability. Regional parties, on the other hand, that could possibly happen, possibly with Presidencies being decided in the House as a new normal. Getting there, though, is another challenge. [A 'No Southern Strategy' could probably create a regional third party that will last a while, but I don't see them or their rebranded successors ever becoming a regionally dominant party.]