The US incarcerates more people per capita than anywhere else in the world except a couple of tiny countries and possibly North Korea (numbers for North Korea, for obvious reasons, are vague, but it probably does incarcerate more per capita than the US). For a developed world country, it has fairly high crime rates (in particular it has by far the highest rate of intentional homicide in the developed world). Like, do you think that there's a magic level of incarceration at which point it would suddenly start working, if only you could get there?