Imo, race is many-faceted and fluid. I tend to agree with those who say it is a social construct. (It would certainly have to be if, as Pioneer claims about blond blue eyed Polish and red haired green eyed Irish people at one time not being considered white, is true!?) I suspect these immigrants were just looked upon as second class citizens.
To me, hair texture is a very good race marker. The nappy black hair gene seems to be a dominant one, and in my experience, a "giveaway" when race is in question.
And surely sociology and psychology should be given as much attention as anthropology when evaluating and deconstructing race.
Since having scientific credentials is obviously not a requirement in this discussion, I submit that blackness can also be a state of mind, a mystique, a certain demeanor, a special vibe, a unique blend of traits stemming from the survival techniques that had their origin within the confines of the slavery culture. That's our identity.
As for the pedigree of America's slave descendant population, we are actually a hybrid breed that could be classified as a subdivision of the Negroid race.
Of course, as Troy is always quick to remind us, the current school of scientific thought contends that there is only one race; the human one. And that our samenesses far exceed our differences.
Kamala Harris has an Asian mother and a Black father. She is, what she is. It's as much about context as about biology.