'Gringo' is an old Spanish word for foreigner, 18th c. or earlier, now mostly supplanted by estranjero in Spain. See previous threads.
Gringo was used in all Spanish and former Spanish colonies for foreigners, in some places applied to the French, or to the English, or collectively; its use in Mexico dates to the latter 18th c. at least, thus has little to do with any of the songs sometimes speculatively related to it.

Wackipedia is not peer-reviewed; many of the statements in it cannot be verified upon examination.