it's not wrong, it's just including the amphibious assault ships the US Navy has as well, which are arguably more powerful than a carrier because they are capable of landing Marines, as well as handling certain aircraft and helicopters. These are probably a more accurate comparison to the aircraft carriers most other countries have.
That graph is outdated too, as the US Navy now has I think 9 of these ships, with another 4 under construction. And add to that another 3 full fledged aircraft carriers under construction.
So yes, the graph is wrong. But not in a way that devalues what the US navy has.