Star Gold gets you lounge access in Europe on a Y ticket, but only for int'l flights. .
ummm..I've flown plenty of domestic flights in Europe with lounge access using *G from United.
Poland, Norway, Germany, Greece to name a few.
The no lounge access on domestic itineraries is purely a US airline thing. Although I am very thankful that at least United is not as bad as AA/DL and have always included Canada as intl.