It'd probably be easier to say what there isn't. I feel bad for you.
What iTunes US
doesn't have:
Albums:
Nothing From Nothing (although, I don't think any of the iTunes Stores have it)
LOVEppears
Duty
(miss)understood
Secret
NEXT LEVEL
Remixes:
ayu-mi-x 3 (NSMM & AO)
ayu-mi-x 4 (NSMM & AO)
ayu-mi-x 6 (-GOLD- & -SILVER-)
Compilations:
A BEST
A BEST 2 BLACK
A BALLADS
A COMPLETE
Singles:
Nothing From Nothing (again, I don't think any of the iTunes Stores have it)
LOVE ~Destiny~
AUDIENCE
SEASONS
M
Talkin' 2 Myself
Together When...
Mirrorcle World
Days/Green
And iTunes US doesn't have ayu music vids.
I'm pretty sure that's it. If any iTunes US users find that I missed something, post it, or tell me, or something, and I'll edit this list.