The one-drop rule is a sociological and legal principle of racial classification that was historically prominent in the United States asserting that any person with even one ancestor of sub-Saharan-African ancestry ("one drop" of black blood) is considered to be black (Negro in historical terms).
This concept evolved over the course of the 19th century and became codified into law in the 20th century. It was associated with the principle of "invisible blackness" and is an example of hypodescent, the automatic assignment of children of a mixed union between different socioeconomic or ethnic groups to the group with the lower status.
It also codified the designation of "white" as an ethnicity.
Plainly, it was and is a completely horrifying and bigoted construct - in a society where "all men are created equal" these sorts of labels are created by the dominant class to keep them dominant and to increasingly marginalize anyone not in said class.
The designations of "Black" and "White" were created by men trying to increase their control. Aside from our believing in the construct, the tailored message of White Supremacy, these labels mean nothing. Especially considering that under the "one-drop" rule, most of us would be classified as "Black" at this point in time.
Further, the propaganda that pits us as "Red" or "Blue" politically is pretty similar. For example, I definitely identify as "Blue" but my views on things like, say, the Second Amendment (I don't trust the government but really don't care for guns) or the legislated removal of certain words (I don't like the words but I like censorship even less) make my Political Coloring a bit more purply.
My guess is that, with the Far Right and Left as exceptions, most Americans could say the same thing - a bit more purply.
The desire to give the rest of us simple-minded choices of who we are and who we "team up" with is manufactured to control the national narrative rather than is reflective of any reality we live within. Slogans like "White Power" and "Black Lives Matter" are intentionally simplistic in the same way that sports teams are advertised. Neither encapsulate the complexities of "White" or "Black" nor the fact that these are simply labels people use on one another to create lines in the sand.
The problems faced by this country are not those of "Black vs White" or "Red vs Blue" but of "Haves vs Have Nots." The more we buy into the separations created by the Haves to divide us up, the more they ending up having. As a nation of non-classifiable amalgams, we would be better served recognizing that fact and uniting our collective efforts in that vein.
We won't, though.
Apple Fanboys vs Android Users
Cubs Fans vs White Sox Fans
Hippies vs Corporates
Millennials vs Everyone Else
We like our binaries here in the Land of the Freaks. We LOVE our binaries. It gives us a reason to fight. And we Americans LOVE to fight.