Liberated indigenous nations, city-state federations, regional warlord territories, whatever you think might spring up out of the U.S.’ ashes.
In a less extreme scenario, California and/or Texas become de facto independent as they just ignore the federal government and their own economy is big enough to run itself. This is assuming a decline of federal power, presumably from frequent labour strikes, mass shootings, bombings and riots. The international influence of the USA declines as the president tries to keep the country from transitioning from the Troubles but in America to full blown civil war.