This is really the topic of George Orwell's 1984, though most people don't seem to realize it. He wrote the book in 1942 (even though it wasn't published till after the war), at a time when the Axis seemed unstoppable. The United States goes Fascist in order to survive, and absorbs England (Oceania). The Third Riech, having conquered Russia is renamed Eurasia, and the Japanese Empire is called Eastasia. There is then a continual shifting of alliances between the 3 to maintain a dynamic status quo.
That is one not unreasonable outcome. There are of course many others. Fortunatly democracy survived the crisis.