There's always room for discussion, but perhaps these topics will answer your inquiry.
Why weren't there any Native-American slaves?
Were Native Americans ever taken back to Europe, as slaves or to be assimilated into European society?
During the period when Africans were enslaved in America, what was the social status like for Native Americans?
Why did Africa become the de facto source for slaves in the Americas? Was there ever an effort to enslave Native Americans?
Why did the early US go to the trouble and expense of importing slaves from Africa instead of just enslaving the Native Americans?
Why were Africans used as slaves in the new world and not the natives?
Did the enslavement of Native Americans still exist at all in the late 18th to mid 19th centuries in the New World?
Were any Native Americans enslaved?