Occasionally writers will prefix a ship's name with an abbreviation of its nationality in their own language, such as "IJN" for Teikoku Nihon Kaigun, but that usage is deprecated.
United States ships that have not been commissioned in the Navy yet don't hold the title of USS, it holds the title of PCU (Pre-commissioned unit)
For example, the shipyard is building the new aircraft carrier-- The Neversail.
For the day the keel is laid to the date it is commissioned, it is called the PCU Neversail. Once it enter active service in the fleet and is commissioned it will be referred to as the USS Neversail.
See also the WikiProject Ships.