To answer the question, “If every state of the USA declared war against each other, which would win?” Quora user Jon Davis went way in-depth writing “the accounts of the Second American Civil War, also known as the Wars of Reunification and the American Warring States Period.” It’s sort of a mix between World War Z (oral histories) and the post on Reddit being turned into a movie (realistic seeming discussion of military action). I am a sucker for this kind of fictionalized future-history stuff.
First came a period of massive migration back to the homelands. Facing the newly invented discrimination that will be created many felt the need to go back to their own people. While the individual states retained all military assets they couldn’t control the individuals who fight. A Texas Marine stationed in California, would not fight for California. A soldier in New York would not fight against their home in Virginia and a sailor in Houston would not fight against their home state of Florida. The warriors returned to their home states and the states had to re-consider that when they measured troop strength of their new nations. Ultimately, they measured troop strength by how much of the population would return home.