alot of reader feel like american cartoon/comics are childish and less creative compare to manga/anime
a lot of the cartoons are. it's the reason why stuff like DCAU/Avatar/Korra gets so high praise. They're ranked along side shyt like ninja turtles.
Comics? Excluding the Big Two.... not so much.
And even Marvel/DC can surprise you.
I'm gradually rereading Jonah Hex right now.
If you think that's geared towards kids, then I don't know what to tell you.
A HUGE part of the problem, though, is that Americans tend to think that if you add gore and nudity that it automatically means it's for grown ups only.
Lot of that shyt is written for kids and idiots, but with gore and nudity as a draw.