Yes this seems super sad as someone from outside the USA. I admit I know little, but I get the impression the police are more self-governing in the US, where as in the UK/Australia there are independent bodies with teeth that can deal with complaints, and even do major investigations across the entire force, such as https://en.wikipedia.org/wiki/Royal_Commission_into_the_New_...

Would a federal level watchdog help? Would it even be possible?

Downvote reasons? Happy to edit the question if it's offensive, dumb, or whatever.