PlayStation.com forum user StalkingSilence found the unopened SingStar site for US. Currently, the site routes you away from singstargame.com to the old PS2 site on us.playstation.com. Using a simple country code substitution, you can see the unopened US SingStore site - which is now LIVE.
A lot of the songs and albums are missing information - they display [Missing text /LBi.SingStore/ID39 for EN-US] - and the ties with your PSN ID are vague, but you can see the information (and initial content) before anyone else!