This list of not the number of different people who go to prison, it's the percentage at any given moment. So a longer sentence will inflate the numbers on this list.
Still, the US has more people in jail than any other country however you look at it. The fact that this is due to longer prison terms is relevant but doesn't change a thing does it ?
I wouldn't suppose that citizens of the US are more criminal than the avg citizen of the world.
It's just that you have the Prison Industry and legalized corruption (see lobbying)
The distinction is quite relevant to the narrative. If your narrative is that the laws and prosecutors unfairly put people in prison that don't belong there, then you want to compare the percentage of people who ever go to prison, not the percentage if people in prison at any given time. The latter fact is relevant to a narrative that our prison terms are too long, but that's a distinct problem.
Also, we do have higher rates of violent crime than our peers. You can't ignore that.
And while its phat to blame the lobbyists, I don't think that's the entirety if the distinction. Americans are simply more retributive than other people. Look at the death penalty. It's 2012 and half the country would be up in arms if the Supreme Court declared it unconstitutional. At the end of the day, prison terms are long because being "tough in crime" got a lot of votes in the 1970's and 1980's.
http://en.wikipedia.org/wiki/List_of_countries_by_incarcerat...
And whether the US keeps people in prison longer than other nations or not, doesn't really help you case IMHO.