I agree with you that J-Pop is starting to be less good. Well, there's still new act like ayaka that is simply incredible. But yeah, it's not that great anymore. I don't think American music is superior though. American music is just not my thing.
I highly suggest you to move over to
K-Pop music! That's what I did after I started getting bored of J-Pop and WOW. I'm so happy I did. I think K-Pop is definitely for you if you like urban stuff.

You'll find great artists like Brown Eyed Girls, Wonder Girls, Epik High, The Grace, Jewelry, Lee Hyo Ri, Rumble Fish, Nell, SHINee and my personal favorite band, Girls' Generation! <3
Maybe I should create a K-Pop download thread.