What you're talking about is cultural as an effort to for the Left to push racial nationalism. The one drop rule actually shows how silly it was because of an inverse of what we currently have.

People who were explicitly white in all but official Mississippi declaration, and were not visibly non-white, were required to allow themselves to be discriminated against. This is basically the whole point of why Homer Plessy sued. There is nothing particularly special about Africans that would make them "unable to blend well with any race". Particularly you bring up Arabs, which are more pre-disposed to violence, inbreeding, and tribalism, explicitly due to Islam.

There is nothing particularly different about their voices, skin, hair, nose, facial structure, proclivities, blood, organs, genetics, phenotypes, etc, that would make them sufficiently different from any other population of humans, including indigenous Americans or Pacific Islanders.

It sounds like you're just back-rationalizing your own biases.