Anime and manga is more sexually creative. Japan in general seems less hung up on sexual fantasy, provided you keep it private.
American creators seem to write sexual content as if they're scared God is watching them jack it, so all their stuff has this frankly cringe sheen
of plausible deniability. Stuff like calling everything a "porno parody", (like "haha, isn't this hilarious? Spiderman and Black Cat fucking?
I'm having such a laugh at this parody you guys, I'm not cranking my hog at all!"), or the whole absurd "step-family" thing.
The most unironically sexy media you'll find coming out the states are probably Rap music videos and old Frank Frazetta or Boris Vallejo paintings.
Anime and manga is just more sexually imaginative and unrestrained. It makes it far easier to cross the boundaries into fantasies
beyond just obvious photo or video documentation of sexual acts, which would then lead people to erotic writings. Like, I can't even imagine
what this site would be like if not for the influence of anime and manga.
And no, I'm not being butthurt over US sexual mores because my story's gotten buried for being about incest, no sir.