USA (or EE. UU.) is an abbreviation that stands for United States. Is used in Spanish to refer to the country whose official name is United States of America (USA). Also if you use u.s. or the original acronym USA (United States of America, see this site), less often.
According to the rules of grammar of the Spanish language, when the word abbreviated to form an acronym is plural, must be duplicated the first letter of that Word. One of the exceptions to this rule is the word ONU (Organización de las Naciones Unidas).
Other examples of abbreviation of Spanish terms in the plural are:
- EE. “Foreign Affairs” (Foreign Affairs)
- AA. “Fuerzas Armadas” (Armed Forces)
- HH. “Human Resources” (Human Resources)
RR.PP. “Public Relations” (Public Relations)
In other languages this situation can also occur. In Portuguese, the abbreviation is the plural for the word, while “Authors” changes to A.A. in the word “pages” the plural abbreviation can also be duplicated “pp.” (or pages). In the English language, in the same way, the abbreviation of “pages” is “pp.”, being that the singular, in both languages, (page or page) will be “p.”.