In the US, the police are essentially an occupying force with their own agenda that they pursue. At times it aligns with the agenda of broader society, but at times not. Because the police know not to mess with the "wrong" people, and because they're generally very well regarded by society, the police unions have considerable power, such that elected officials are often terrified to reign them in. A good example of this is NYC where hundreds of cops turned their backs on the mayor and basically accused him of stoking violence against the police after he was mildly critical of them. This was a huge news story[1], and the mayor has refrained from criticism since then.

1: https://time.com/3644168/new-york-police-de-blasio-wenjian-l...