I think that thanks to the internet and pseudo hive minds of Gen Z (or millennials?) and younger, human society will remain mostly stable for the foreseeable future. There will be civil unrest and power transitions, but our technological civilization is on the brink of becoming immortal within the bounds of time.

So maybe the US government will collapse (hopefully), but it will be replaced by something quite similar. Just as it was a replacement for older forms of governance, derived from the old Roman and Greek republics.

It already has. You would not understand a man from 1500 England, and you might barely understand some AAVE, Jamaican Patois, or Scots speakers of today