The USA has some of the worst human rights on earth, as evidenced by their massive prison population.

They don't need to because cops can just flat out murder people off the streets. And brownshirts are a thing too they show up at protests to harass the strikers. Also they're not under an active genocide (as much as they try to feign that they are) so there isn't a lot of violence gas to go ham with.

You have a point. Though the US white supremesists haven't launched such organized and open assaults. So maybe it just scales with human rights abuses.

US white supremacists genocided countless Indian tribes. They also rounded them up in reservations and then enforced policies designed to kill them. Look up the Trail of Tears sometime.

There's also the terror campaigns waged by the various Ku Klux Klans and other organizations against African-Americans.

If you want something more recent there's also the Tulsa race massacre. There's also the many, many deputy gangs in the US. Those launch organized and open assaults against other Americans all the time but they're also very distributed so we don't have one big incident to point to.