So there was a TV miniseries back during Reagan in 1987 called Amerika which basically amounted to - in a "future scenario" at the time - the US had been infiltrated from within by the Russians for decades and eventually were officially invaded.
Up until the invasion, the Constitution and all the US' daily lives were still as they normally were to the public, but once it got far enough to admitting the system was phony they changed the US flag to include the hammer and sickle, split the country into districts, mowed down Congress in the Capitol, and killed all citizen dissenters.
It's pretty much been memory holed since then - gee I wonder why - and fuck if I can't find a more applicable scenario to our current events, whether it be the Russians or the Chinese.