When people see an abbreviation, many refer to it as an acronym, thinking they mean the same thing. They don’t.
You all know what an abbreviation is. An acronym is also an abbreviation—but one that is pronounced as a word:
Snafu ( it lost the caps when it became a common word)
MOMA in New York and LACMA in Los Angeles
You’d never say “Oosuh” or “Yoosuh,” so USA is not an acronym, just an abbreviation.
All acronyms are abbreviations, but not all abbreviations are acronyms.
(If you’re not sure what snafu and fubar stand for, look them up in your online dictionary; there you will discover the slightly off-color meanings.)