This is an easy answer....the US military does tons of training. Your local cop might do twelve hours a year of training....mostly just getting forty rounds and firing them away at some range within the county. A US Army private gets lots of training....something that local cops can’t afford.
The PDs could sure afford all those MRAPS and tacticool gear though, now couldn't they?
Maybe they should worry about training for ROEs, using common sense, and dealing with the public rather than loading up on the latest military gadgets.