My Album in iTunes Says "The Item You've Requested Is Not Currently Available in the U.S. Store."

Congrats! This means that your album has been successfully delivered to iTunes, and they're in the process of making it live in all iTunes stores across the world. Albums sometimes go live in your country after a few hours, and sometimes a few days. Only thing to do now is wait.

There's nothing else DistroKid needs to do at this point, as your album is safely in Apple's hands now. 

A note regarding pre-orders on iTunes:

iTunes links default to Apple Music on mobile, where the release won't be available until the actual release date.

You'll still be able to find your pre-order in the mobile and desktop versions of iTunes, though.

You can also try adding ?app=itunes to the end of your iTunes link, which may help force mobile devices to check iTunes directly, rather than Apple Music.