This isn't D&D, this is history. But if you want to understand how America ultimately collapses, and why it happens, and what that fall ultimately looks like - whether it happens in twenty years or a hundred years - the history lesson is available. This is the first part of six for the 1983 series, The Spanish Civil War, narrated by Frank Finlay (who some will know played Porthos in the 70s Musketeer movies):
You should watch the entire series, which is available on google. Pay very careful attention to Franco's employment of the Moroccan colonial army, and how it was used to control the home country. Then scoff at a future American government's use of future colonial Iraqi, Afghan, Colombian and Congolese armies to subjugate 'good' Americans. Tell me about how it could never happen.