Especially given that the two political parties include 2/3rds of the population, there's no way your preferred conflict would be limited. That's not even counting what hostile countries and non-state actors would do to us while we're tearing apart the nation. What do you see as the end state after the two parties "get the knives out on each other"?

Given that this is how people always organize themselves in the post-monarchical period (significant counter examples welcome, but of course one party states don't count), it's fatuous to imagine that we'd see anything in the vague direction of the Founder's idealism (well, I'm sure some realized they'd develop, as they did rather quickly, especially after Washington left the national stage (heh, which I drafted before seeing your addition)). After those knives spill enough blood, it's doubtful there'd even be a reconciliation.