I have one reservation about this. Would Warren have used American Indian in 1986. Then the preferred appellation was Native American. Today it is Firdt Nations of the Canadian Indigenous Peoples.
I think Indian was still used in 1986. I can’t say when its use faded away though.
Reminds me a bit of how the use of Negro faded away. Martin Luther King spoke of conditions for Negroes, the status of the Negro, etc. up until he died in 1968. It was sometime after that, that Negro fell into disuse. By the early ‘70s the term Negro wasn’t being used at all.