Hate to say it, but you have to define it...
Today, "African American" is a census category that is, essentially, self-selected...
As has been said, the only things the US goverment continues to define by blood are horses, dogs, and Native Americans/Indians.
The last is for reasons that have as much to deal with internal tribal politics as national, of course, so as odd as it sounds today, it will presumably remain a matter of public policy.
And given the increasing levels of emigration from post-colonial Africa to the US, there's an inherent question.
Best,
Yeah, the whole identification as Native American includes actively practicing tribal rituals/culture and stuff like that. My son is adopted from Guatemala and any idiot can clearly tell from looking at him that his ethnic makeup is more Mayan Indian than anything else but ethnically he is considered Latino, not Native American.