What about the 1-3 million people in Chinese concentration camps (excuse me, "re-education camps")?
[1] http://www.jpolrisk.com/brainwashing-police-guards-and-coerc...
[2] https://www.reuters.com/article/us-usa-china-concentrationca...
[3] https://www.nytimes.com/2019/05/04/world/asia/trump-china-ui...
Second, while America has a serious prison issue (the highest incarceration rate in the world? really??), the current state of affairs of African-Americans isn't really comparable to the treatment of Uighurs, Tibetans and Falun Gong practioners.