The Royal Spanish Academy has long recognized that words unique to places such as Mexico or Bolivia are "real" Spanish. Now it has acknowledged that some words peculiar to United States Spanish can be genuine Spanish as well.
According to various press accounts, such as this article from Noticieros Televisa of Mexico, the Academy recently added the word estadounidismo to its dictionary with this definition: "Palabra o uso propios del español hablado en los Estados Unidos de América," word or use peculiar to Spanish spoken in the United States of America. (If the use of the plural propios sounds ungrammatical, it may because you're unaware that two singular nouns joined by o can take a plural verb in Spanish.)
Examples of such "U.S.-isms" include parada to refer to a parade, instead of desfile, and aplicar to refer to applying for a job, rather than solicitar.
The article referred to above distinguishes between estadounidismos and Spanglish or espanglish, defined as a mixture of Spanish and English elements, although the Spanglish example of using carpeta for "carpet" doesn't seem to be much different than the usage of parada. Apparently, uniquely U.S. usages may be accepted as Spanish as they become used in the written and published language.
According to the article, the Academia Norteamericana de la Lengua Española is putting together a list of U.S.-isms for future inclusion in the Academy's dictionary, which is broadly viewed as authoritative.