I doubt they are corrupted compared to other countries. In south America it's common to give a propina to the policemen so they forget you. Let's forget about Russia where they arrest you to ask you money. I don't think it's the case in the U.S.

The only thing I find weird with the U.S. system according to reddit is that police officer (at least the one with a higher rank) don't need to get degree in law. (Here we have police men with limited legal power and no special degree required, then officer who need a bachelor in law -or climb the ladder through experience- and can lead investigation, arrest people, and commissioner (master of law or climb the ladder trough experience) who as a junior run a police station while senior have job like regional management of the public security)