Mexican vs Central American

Mexican and Central American both are nouns.

Word	Noun	Adjective	Verb	Adverb
Mexican	Yes	Yes	No	No
Central American	Yes	Yes	No	No

As nouns, Central American is a hypernym of Mexican; that is, Central American is a word with a broader meaning than Mexican:

Mexican (noun)	Central American (noun)
a native or inhabitant of Mexico	a native or inhabitant of Central America

Mexican (adjective)	Central American (adjective)
of or relating to Mexico or its inhabitants	of or relating to or characteristic of Central America or its people or languages