Acording to a post in ZIV (that was taken from one of the SN2AC developers), the following songs were made by the american team (which may or may not include recently hired members such as Dukamok):
-A thing called LOVE
-Trust -DanceDanceRevolution Mix-
-Blind Justice
-Angelus
-Me Against the Music
-switch
-CaptivAte ~Chikai~
-volcano
-Venus
-Pluto Relinquish
I'm quite proud of our national stepping team
.
Regarding the xbox games, I like how they have a lot of challenge charts for most of their songs and take care of players who want the extra challenge as opposed to the japanese-brewed games, that after you've taken care of 90% of the game (mostly 7's and 8's) you are left with pretty much nothing but the boss songs that, while challenging, get old fast since it comes down to playing the same 4 or 5 songs over, and over, and over, and over...
ITG was supposed to do that (what the xbox team is doing), but it seems that all the effort went to the Expert charts while not so much was put into Hard, even less into the lower difficulties, which is why ITG is so popular among the hardcore crowd but DDR easily retains the casual crowd with quality charts on every level.