This has come up before but I don't think we've come up with many examples you haven't listed. And even 12 Years A Slave is American in the same way Lord Of The Rings is: predominantly non-American cast, directed by an non-American but produced by an American company.
A few I'd like to at least see on the ballot would be Within Our Gates, Malcolm X, Mo Better Blues, Hollywood Shuffle, Sorry To Bother You, and (very far outside chance) Black Dynamite. I've never seen it but I always hear The Learning Tree is very good.
Also, Sixth Sense is directed by a person of color (though not black and I'd say maybe not deserving of being on the list). But everyone forgets it, I'm assuming, because the cast is white.