American flag vs Star-Spangled Banner

American flag and Star-Spangled Banner both are nouns.

Word	Noun	Adjective	Verb	Adverb
American flag	Yes	No	No	No
Star-Spangled Banner	Yes	No	No	No

As nouns, American flag and Star-Spangled Banner are synonyms defined as:

American flag and Star-Spangled Banner: the national flag of the United States of America

Other synonyms of American flag include Old Glory, Stars and Stripes.

American flag (noun)	Star-Spangled Banner (noun)
the national flag of the United States of America	the national flag of the United States of America