usage vs Americanism

usage and Americanism both are nouns.

Word	Noun	Adjective	Verb	Adverb
usage	Yes	No	No	No
Americanism	Yes	No	No	No

As nouns, Americanism is a hyponym of usage; that is, Americanism is a word with a more specific, narrower meaning than usage:

Other hyponyms of usage include Anglicism, Britishism, consuetude, couvade, Germanism, habit, use, hijab, rite, ritual.

usage (noun)	Americanism (noun)
the act of using	a custom that is peculiar to the United States or its citizens
accepted or habitual practice	loyalty to the United States and its institutions
the customary manner in which a language (or a form of a language) is spoken or written	an expression that is characteristic of English as spoken by Americans