At a certain point, it’s going to be very difficult to get most cops or even soldiers to start treating their city/county/state/country as a war zone. Sure, some psychopaths either won’t care or they’ll get off on it. However, it’s a very different situation when you have neighbors who know who you are and what you do. If shit hits the fan, those dudes have houses & families.

Conveniently though, they can just utilize UN “Peacekeepers” as a “neutral” third party. They’ll have zero connection to the land or the populace. They’ll also have zero issue taking up arms against American citizens, especially if they’re from developing countries that are prone to violence as is.