Are cops in America really that proficient with guns tho? Most of them probably only spend as much time in a gun range as an average gun owner, and quite a few probably only spend whatever minimum time is required by their department. Also only a minority of them will ever fire their weapon in the line of duty, and unless they work in Baltimore or something it will probably only be once or twice in their entire career. Police involved shooting are actually quite rare, and half the time they're as likely to shoot each other along with everything else when they unload at whatever hostile they're confronting.

I'm not trying to denigrate cops over this, I don't particularly want a police force that's a trained paramilitary. And certainly sovereign citizen types wouldn't win in any kind of armed insurrection at this point, but I wouldn't put it down to LEOs weapons proficiency as the reason.