If you say the monopoly on violence is the issue with the US’s police violence issue what you’re saying isn’t that the police should be controlled better in their deployment of force, you’re saying that individuals should be able to shoot back at the police or, in fact, at anybody else they don’t like.
I’m saying in theory the monopoly of violence is given mandate through elections, and in the US those winning elections do not always do so by being the most popular. It’s an issue that goes higher than the police as the monopoly is transferred to those without an actual majority of support. The President is commander in chief of the executive branch, that includes the cops. The problems are coming from the top down. It’s considerably different than any of the other countries you mentioned.