American spelling vs overemphasize

American spelling is a noun but overemphasize is not a noun.

Word	Noun	Adjective	Verb	Adverb
American spelling	Yes	No	No	No
overemphasize	No	No	Yes	No

American spelling (noun)	overemphasize (noun)
English orthography used in the United States (characterized by 'analyze', 'center', 'usable')

American spelling (verb)	overemphasize (verb)
	place special or excessive emphasis on