I don’t think open conflict is likely between the “reds” and the “blues”, but I would say that any such conflict would at least have an economic component either exclusively or in tandem to armed conflict. It would be interesting to see the economic Nash equilibrium of such a conflict.

All that said, the international scope of American polarization is also worth consideration. Russia had a trifling investment in social media to have major say in the ultimate deployment of US forces from South Korea to Syria. The current tariffs via China, Europe, and Canada target red states/counties disproportionately. The economic element is significant, will be the first thing felt by most people, and doesn’t receive enough coverage.