USN system is standard in In US and NATO countries, but its not worldwide standard, not used in Russia, not in China and not in many other individual languages.
Im gonna make a comprehensive list of each abbrevation, where it comes from, how its translated and what the designation means
The USN system is not the NATO system.
The USN system is used by the USN, the JMSDF, the RAN, the RoCN, and I think the RoKN. The NATO/Commonwealth system is totally different and maintains unique pennant numbers for every ship in all of the navies that use it.