There are a couple more alternative variant labels I've found in my collection:
A USA-2 seems to exist for ATV: Quad Power Racing. The software is the same (no revisions). The USA-1 looks identical to the USA. But the USA-2 has Crave.
Then Polly Pocket: Super Splash Island is not a USA-1, but actually has two distinct labels:
As far as I can tell, the only difference in-game is the logo screens at startup.