But incarceration rate per population doesn't tell you if the population is being over-incarcerated unless you know the crimes-worthy-of-incarceration rate. If America's rate of crime-worthy-of-incarceration is several times the European, then it's perfectly natural the US has a several-times-higher incarceration rate.
Now, there are all sorts of difficulties in calculating such a rate. But it doesn't seem too unreasonable to guess that, however it's calculated, the general rate of crime-worthy-of-incarceration would correlate with the homicide rate. So, let's use the homicide rate as a normalizer. How many incarcerated persons does a country have per annual intentional homicide? Using the Wikipedia numbers for prisoners and annual intentional homicides, we get:
Czech Republic: 163
New Zealand: 203
South Korea: 109
Thus, the US incarceration rate differential is within the normal variation seen in developed countries, after you account for the fact that the US has a lot more violent crime than other developed countries (as seen in its much higher homicide rate).