You probably can't do anything about the actual prison experience, but you can help the individuals both before, during and after.

There are organizations that try to keep people out of prison by giving them activities or trade training.

And there are organizations that try to help people find jobs after leaving prison.

You could find some you like and help them financially.

Another positive influence is the religious community, so you can help those as well. People with strong religious ties tend to have a much easier time joining their community after prison.

There are also some religious communities that try to reach people in prison, and you could help them.

I think (as non-american) that the best you can do is to try to convince your American friends (you may have to acquire them first) that the idea of the prison is not a punishment but isolation of the danger and reconditioning to the return back into the society.

My understanding is that the last one can not happen in open prisons but only in solitary confinement where a single prisoner does not have any contact with other prisoners but still has constant concealing by professionals and does have other conditions to maintain its decency.

Nuke us.