> So far when I research the alleged problems with the US prison system, I learn they are also generally present in other prison systems.

The difference is probably the degree of abuse and cruelty.

Also, the U.S. seems to claim to be a civilised society, so it would make sense to compare its facilities (including prisons) with those in other "civilised" societies. When you do that kind of comparison, you may be shocked to discover that U.S. prisons are amongst the worst.