The executive in each state controls statewide police, in smaller jurisdictions either sheriffs are elected or appointed by the executive.

This is true, but rather undermines the original point about the POTUS doing it.

State governors and city mayors tend to be a lot more willing to do things like this, but you'd still have to get the political will. I'd expect you'd need someone to successfully get elected on a platform of doing it, and for the opposition to not find it reasonable to attack that item on the platform.