American bison vs bison

American bison and bison both are nouns.

Word	Noun	Adjective	Verb	Adverb
American bison	Yes	No	No	No
bison	Yes	No	No	No

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

American bison: large shaggy-haired brown bison of North American plains
bison: any of several large humped bovids having shaggy manes and large heads and short horns

American bison (noun)	bison (noun)
large shaggy-haired brown bison of North American plains	any of several large humped bovids having shaggy manes and large heads and short horns