Civil wars rarely happen in a vacuum. They almost also involve, often are caused by, and always made worse by - outside actors.
The collapse of the Soviet Union would be the most analogous and potential BEST outcome of such a scenario in the USA, and even then - it became 15 countries, lost half its economic output, has been fighting constant wars since, and has NATO and China on its borders.
I don’t think the majority of Americans have 10% of the resilience of the Russian people either.
Civil Wars are only possible when the elites of different regions have irreconcilable differences.
In the United States the elites are united in their effort to rip off and crush average folks—they have nothing to fight about...