japan isn't as economically impoverished as other asian countries so a lot of guys like to delude themselves into thinking that they'll like you for you, but a lot of japanese girls have silly ideas about white men and american culture and are all gung-ho to hop on board. but when reality sets in, they may choose to flee back to japan or dump you for a japanese guy (i've seen it happen too many times to count), and i know plenty of horror stories of jgirls' behaviour turning 180 after marriage.
also, you don't have to rip into american women like that. you'll meet plenty of air-headed japanese girls who don't know their heads from their asses, especially the ones who chase gaijin. and don't believe those stories about you being hot stuff just because of your pasty skin-- those days are long gone. most white guys i knew while i was on exchange were unable to hook up.