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.
It’ll be kinda like the collapse of the Empire in the Foundation trilogy I think. Just a gradual loss of hegemony followed by a swift turn inwards of the remaining power of empire (as the labor of the colonies begins to break free of colonial control).
As the ties to the global south begin to sever, the capitalists will start to turn inwards and the USA will consume itself. What comes out will be determined by the nature of the consumption, either some form of fascism that will mobilize the reserve labor of the core into a new, more brutal empire, or popular resistance and the proletarian revolution we were always told would happen in the developed countries. Either way, the US as we know it cannot continue to exist as it currently is.
it’s already balkanized, and balkanization is built into the system.
I’d be very interested if you wanted to expand on that thought a bit more.
remember the first episode of Star Trek the Next Generation?
