The point is to keep escalating until the government cannot just keep throwing cops at the problem. This, however, requires some level of popular support, which does not seem possible given that about half the American electorate is fine with slavery in the first place.
Concentration and extermination camps are two different things (and Auschwitz illustrated that clearly after 42 and the Birkenau camp).
A very quick glance at what happened at the US-Mexico border makes me think the camps there fit the bill, or at least the usual definition of the word (basically, indiscrinate mass internment).