Hentai - Illegal in America?

So what's this about hentai being illegal in (North) America now? What constitutes an animated image being considered underage? Does it refer to teenagers as well as loli? And, if yes, what's the criteria for judging that? Help me out, world4ch, I need answers.

Loli/shota is legal on a federal level but it is ultimately up to the state to decide. A friend of mine is locked up for a LONG time because he crossed state lines with that shit. His name was Robert Paulson.