WineCountryUA

Generally no.
UA offers Complimentary Premier Upgrades for most flights in USA, Canada, Mexico, Central America, Northern South America, Caribbean, ....
But long haul international -- TATL, TPAC, intercontinental, .... require supported upgrades: miles+copay or PlusPoints

There is the rare case where economy is oversold and the upgrade waitlist is shorter than the open premier cabin seats, airline will do operational upgrades (Op-ups) and status can help. This are very rare.

For upgrades no, but UA Gold provides lounge access for international trips.