Hi
AFAIK the rule is UA (and now US) *G members are only allowed access to the RCC within US - (a) if they have paid membership of RCC, or (b) as a domestic leg on the same itinerary as international flight (or could be same day and same itinerary?)
But
Fliar, IIRC you are *G on other program, so you should have access to *G lounge regardless. You may need to argue with attendant to let you in - having a printout of relevant rule will help. See the rules on
www.staralliance.com for example.
I am sure there are other threads on US domestic lounge access for overseas *G's - perhaps on the US forum (given *A is new) or *A forum?
Cheers