If something like this ever happens, the troops will shoot citizens.
Happens too frequently with friendlies and US troops in history.
Also, sadly, 85% of our population will do exactly what they are told to do without asking questions.
Only 10% will think about trying attempting to think on their own, but only if they don't get into trouble.
The remaining 5% of us will recognize that we are the masters of our own destiny, and depend upon nobody else for help, as they probably could not be trusted anyway.