I definitely agree with your comment. But for the sake of the discussion, I would like to point out that Europe also has prison problems, but at a way lower scale:
- UK's Belmarsh prison has been criticized extensively and regularly compared to Guantanamo: http://news.bbc.co.uk/2/hi/uk_news/magazine/3714864.stm. As an aside, Julian Assange spent the past 1 year there.
- France and Norway prisons have very high suicide rate: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6066090/. Though no country is even close with the USA. Citations from the article: "We excluded the USA in one analysis (for incarceration rates) because it was an outlier, with an incarceration rate of more than eight times higher than the majority of other countries." and "Rates of prison suicide compared with rates of incarceration - Data are for men and women combined. USA was not included in this analysis because it is an outlier (appendix p 17)."