American spelling vs American English spelling

American spelling and American English spelling both are nouns.

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

As nouns, American spelling and American English spelling are synonyms defined as:

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

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