JAV does the whole "schoolgirl" thing a whole lot better. When they do it in American porn the number one thing is the uniforms aren't realistic and there's not much variety. The whole "sexy schoolgirl" uniform of the too-short skirt, crop sailor top, stockings and high heels doesn't appeal to me. I want them to look like they still might be in school, even though they're clearly too old to be in school.
The other thing is that JAV actresses appear more natural, even if they aren't, and they're not covered in tattoos. It's hard for me to buy that a woman still goes to school when she's wearing high heels, has fake tits, and is has tattoos.
JAV also caters more to people like me who have a one-piece swimsuit fetish; that's how I got into the genre in the first place. Western audiences aren't really all that into one-pieces.
You're touching on something which for me is a very important advantage for JAV. They dress their women in real world clothing. Sexy real world clothing, but real world clothing nonetheless. Every one of these archetypes they present, whether it is school girl, teacher, office worker, housewife, flight attendant, etc. looks like someone you might see in that role when going about your daily life. You might think, damn, that's a short pencil skirt, or, look at those huge boobs in that tight, sleeveless top, but you're never going to wonder why they aren't being arrested for public lewdness based on how they're dressed.
The American approach kills the fantasy. Just as an illustrative example, years back I downloaded a vid with Brooke Adams, who at the time was a popular US pornstar. It interested me because she is a cheerleader in the video as I still had some cheerleader fantasies in me. First scene she is walking up to some guy's door to sell him something, and right off you notice something odd: the back of her skirt is
missing. First thing I thought was, how is she going around outdoors like that? Second thing I thought was, that doesn't look like any cheerleader outfit I saw when I was in school. All this mentality does is constantly remind you that you're watching porn, which kills the fantasy.
A fantasy in American porn is not something to be developed on screen. It's really just a box cover lure. It's always discarded in minutes, and the rest is just the same sex acts you see over and over again.
Oh, and another thing I didn't mention in my earlier post in favor of JAV: the absence of tattoos!