We've been worse than modern Canada and China since at least the 1930s. Wild.
Estimates vary wildly on how many people were executed, starved to death, murdered, or imprisoned during all of the Chinese Revolutions under Mao.
I'm certainly not defending the America prison system.
Yes, but he also didn't add the massacres and concentration camps for Native Americans (of which, Hitler writes in his Main Kampf that it was an "inspiring" solution to the problem), or the enslavement (any different than prison?) of black slaves, and their executions, lynching.
And, arguably, it is better, because it may mean that we have made some moral progress.
As for the blacks, the legal system offered segregation until the sixties and the infamous "Jim Crow laws".