I was travelling a few years ago, and hanging out in the hotel bar in Portland, Maine, and I listened in on a heated conversation between some guy and a lady whose husband is a cop. They were discussing police brutality and the protests at the time (Baltimore maybe?), and the lady's point was basically "do whatever you want with regulating police behaviour, but I will take my husband coming home at the end of the night over anything else"
It's possible with the falling rates of crime, this may just solve itself (though increasing police training and standards is a good thing regardless).
US Police is above the law.
They can and do break most any law at will, without consequence.
Any "Law & Order" fan will tell you crime needs to not pay for people to behave civilized. For US Police, crime does pay.