There's probably a limit on how many men are willing to be Gestapo, well probably hit that first.

Economic activity must lessen or even halt when under siege. We lost about 0.3% of the US population to COVID and had labor shortages and supply chain problems for years - can't disappear and deport too many folks.

I'm actually surprised that the NRA types haven't risen up against tyranny. That would be a real problem.

A lot of sieges happening at once will end up as a command economy, which leads to market distortion. Prices and availability problems ensue.

Any or all of these things could lead to a quick societal collapse. Trump is wrong in believing that people will just carry on as before even when all manner of changes occur. At some point, people change behaviors in n response.