It's worse than that.

First, is it correct that US has lost the top spot in the last 3 years. But this only counts prison population.

The US parole and probation system is twice as big as the prison system. Under the parole and probation system people are monitored by cops regularly, their wages are garnished, they have obligations to report to court, to officers, to the state.

That means the criminal justice system in the US is managing criminals at 3x the per capita rate as any other country. Sure, the prison population ebbs and flows a little, other countries edge higher temporarily, but the US total system is massive beyond belief.

Then there's recidivism. The US is in the top tier for recidivism rates. There are a few other countries that compete with the USA, like UK and Brazil. But none of them couple their high recidivism rate with the massive incarceration rate nor with the gargantuan parole and probation rate.

And then there's pay-to-stay. In the US a large portion of prisonerd are levied a day rate for being in prison, between $100 and $400 depending on the state. No one else does this. People leave prison with a massive debt to the state, which is why the end up on parole or probation, and why their post-incarceration wages are garnished.

It's a brutally sick system. That dwarfs everything in existence, even if some other systems come close on a single metric.