Remember this next time a person says "but labour camps, tho".

So even if you take the highest estimate from the US State Department, the DPRK has 120k prisoners with a population of 26 million. The US prison population is 1.8 million* out of a total of 332 million. My calculator says that's 0.46% vs 0.53%

*This doesn't include the 3 million or so under parole or house arrest.