Prisons in a lot of countries are a lot better, countries in Europe, South America, all have better treatment of prisoners in terms of rights. America under the US Constitution actually views prisoners as slaves, and this is not debatable.

Of course you can find some prisons in some parts of the world where prisoners are treated much worse but I didn't say America has "the most harsh" but I said "some of the more harsh". In some other countries prisoners actually have human rights, aren't viewed as slaves, and even receive Internet access.

References

1. https://www.aclu.org/other/abuse-human-rights-prisoners-united-states-solitary-confinement
2. https://en.wikipedia.org/wiki/Internet_in_prisons