Might want to read your own link there homie.

Starfleet used the “USS” designation on certain computer graphics for United Earth NX-class starships, such as Enterprise NX-01 and Columbia NX-02. However, they did not label the hulls of the starships, and the ships were not commonly addressed with the prefix. (ENT: “Divergence”)

On Federation starships operated by Starfleet, the “USS” prefix was more prominently featured on the hull of the ship and as part of the starship’s official title. USS was referred to as standing for either “United Space Ship” (TOS: “The Cage”, “The Menagerie, Part I”, “Space Seed”, “The Gamesters of Triskelion”, “Patterns of Force”, “Assignment: Earth”, “Elaan of Troyius”) or “United Star Ship.” (TOS: “The Squire of Gothos”, “Court Martial”) This designation was used as early as 2167 on a Daedalus-class starship, the USS Essex. (TNG: “Power Play”)