The goal in Europe is integration and eliminating recidivism, whereas the goal in America is vengeance and isolation. You won't see any progress until that overarching goal changes.
Another issue is how the government + private industry is allowed to punish you for life even though you've supposedly "done your time". Employers can and regularly do discriminate even for things that would have no affect on job performance. Oh also housing and loans. You're basically pushed to the fringes of society unless you manage to make it big with your own business.
Oh and if you commit a drug crime you're cut off from school financial aid for life. And if you have any felony the army probably won't even take you. Have fun trying to turn your life around when your own government slams the door.
I'm okay with long prison sentences for really nasty stuff like murder. Not such a big deal if an ex-con steals some shit again, pretty bad if he goes back to killing people.
Given the way American politics runs on lobbying, I'm inclined to lean towards the goal actually being maximizing profits. This can appear in various ways:
Private prisons lobbying for longer sentences, and service providers monopolizing service to prisoners to charge exorbitant rates: https://www.newyorker.com/business/currency/making-profits-o...
Training voice AI on prisoner phone calls: https://boingboing.net/2019/01/30/prison-profiteering.html
Even profiteering on halfway houses: https://www.prisonlegalnews.org/news/2018/mar/6/cages-commun...
And others. Just look up "prison profiteering" and you'll find endless examples.