The reason for your confusion is that United and US Airways have the cheapskate policy that their own *G customers (eg 1K and PremEx) cannot access their own lounges without a paid lounge membership, unless they have a same-day international flight. Happily, this situation does not exist anywhere else in the world (and ironically, all non United or US Airways *G customers can freely access the unparalleled joys of Red Carpet Clubs and US Airways Lounges even on solely domestic US itineraries).