Ok, the abbreviation for the United States is EEUU or El Estados Unidios…what does the final “U” mean?
EE and UU are plural abbreviations for ‘Estados’ and ‘Unidos’ respectively. English does this occasionally as well: consider pp. for ‘pages’.
Yeah, it comes from Latin (maybe Italic) and is carried on in Italian, Spanish and French (?).
Yes, there’s no “El.” It would be “Los Estados Unidos.”
“Estados Unidos” as the name of a country is singular and, being a proper noun, uses no article.
Sin embargo, I’m often asked, “Es/eres de los Estados Unidos?” I’ve never been asked, “Es de Estados Unidos?”
Feel free to correctly respond “soy de Estados Unidos”.
Your cite is from the style book of a newspaper, El Pais. While this is commonly used as a style book (and we are using it as a guide for a bilingual exhibition I am currently working on) it’s not the final word on usage, any more than the AP or University of Chicago stylebooks are for English.
A more authoritative cite is from the Real Academia Espanola (Spanish Royal Academy), which states:
This says that the name may be used with or without an article. If the article is used, the name is considered plural and takes “los” and a plural verb. If the article is not used, the name is considered singular and takes a singular verb.
Certainly “los Estados Unidos” is a very common usage. I get 18 million Google hits for it, including the sites of US embassies in Spain and Latin American countries.
Hey, sailor, since you’re following this thread, which do you think is better: americano/a or estadosunidense? I learned the former in Spanish class in school, but I’ve seen the latter in the Spanish-language paper in Chicago.
My link contains the opinion of the Real Academia on this issue:
Personally, I think estadounidense is fine, but Latin Americans tend not to use it in preference to norteamericano. While I understand the objections to americano, using such an inaccurate term as norteamericano does not seem to me to be a good substitute.
I am not saying using the plural for “Los Estados Unidos” is not used but I do say the singular should be considered more correct as it is a proper noun, the name of a country. Like a company name or other collective name can be used in both singular and plural and there might be a slight nuance but when referring to a corporation as a single entity I believe it is more correct to use the singular: Microsoft has launched… Same with Estados Unidos.
With respect to americano / estadounidense … I really do not have strong opinion and I suppose it depends on context. Americano is just simpler and easier and is favored unless estadounidense is needed to avoid misunderstanding or ambiguity.
Seems to me like “Unidos” is not plural. Just like “United” is not plural.
“Unidos” is definitely plural and I would think “United” is plural too. Like “white” in “the cars are both white” is plural.
That’s because you are using English grammar to try to understand Spanish. In Spanish, plural nouns take plural adjectives.
You are trying to use Spanish grammar to understand English. In English, adjectives are (usually) neither plural nor singular.
You are free to think whatever you want, but the Real Academia, the official authority on correct Spanish usage, disagrees with you. They do not indicate that either usage is “more correct” than the other. Both are completely correct in Spanish.
In my personal experience, in Panama “los Estados Unidos” is by far the more common usage. Usage may differ elsewhere. However, this is the term used by many official sites, including US embassies in Latin America as well as Latin American embassies in the United States.
Depends on what you mean by “favored.” It is true that many Latin Americans will casually use the term americano for a US citizen unless they are trying to make a political point. The Real Academia, however, recommends that this term “must be avoided.”
In actual fact, what I am usually called is simply “el gringo.” 
I’m Hispanic but have never encountered “unido” as apposed to “unidos”. It takes two or more entities to be united, no?
I’m very surprised by that. It depends on whether the noun is regarded as singular or not. Very well-known examples include the Reino Unido (United Kingdom) and the song El pueblo unido jamás será vencido.
Yep, a single entity united from within. Makes sense.
(bolding mine)
I guess it’s possible, but I can’t think of a single instance where we’d use this form in French.