Part of the problem is probably that in the USA you can be locked up for sneezing. It's common for normal people to have been jailed for something at some point in their lives, who would never have had any brush with the law in another developed country.

Another contributor is this: https://en.wikipedia.org/wiki/Poverty_in_the_United_States

There are relationships between incarceration, poverty, and class and race struggles.

(How about the fact that something like 40% of the prison population consists of blacks? Looks like the effect of "War on Black" more than "War on Drugs".)