Bad officials unwilling to prosecute bad cops is a second symptom

Apathetic electorates electing bad officials unwilling to prosecute bad cops is a third symptom

Municipalities spread all around the country are suffering from the same combination of symptoms. Whether that suggests one national problem or the same local problem in replicate is a question of semantics.

Well, no, we nationally have gay marriage because of federal court decisions voiding state actions prohibiting same-sex marriage as violations of the federal Constitution.

And we don't have legal marijuana anywhere in the United States (we have states which have chosen not to layer state prohibition on top of federal prohibition for some acts involving marijuana, an federal law mandating deferring prosecution for certain acts involving medical marijuana that are consistent with state law. Anyone who actually makes significant money in marijuana would still be subject to the federal drug kingpin laws were the policy deferring prosecution ever to be lifted, and technically without that if any part of their business involved any acts not entirely within the required deferral of prosecution.)

No, "let Democratic State governments of the Southern states handle it" was how America went through Jim Crow laws. Localities would never have gotten away with it if the State governments had not supported them and helped them crack down on local citizens who pushed back.