Fourth alternative, chaos. I believe the US will become more like Mexico with drug cartels, various maffias, enthnic break away states etc carving out chunks of the country. The US government isn't going to go authoritarian, the US government is increasingly weak, corrupt, ineffective and without legitimacy. I don't believe there will be a formal civil war or succession of states, I believe there will be massive riots, white people leaving cities, drug cartels acting more like the way they do in Mexico and gangs taking over places. In white towns local leaders will start to play a bigger role. The government might not be able to fix the roads or manage things but a local strongman such as a business owner, the local sheriff, some low level politician etc might call for meetings in the town hall and start organizing people to fix things

Another potential situation is Russia in 1993. Russia is also a large multiethnic empire and it descended into violence and wide spread dysfunction. The difference is that the Russians are more used to that situation and therefore have a tradition of strong autocratic leaders while it would be much more difficult for the US to get a Putin or Xi Jinping.