American racialism made Black assimilation impossible and therefore historically irrelevant

Evidence

On the other hand, the drift toward assimilation to the Europeans by a fraction of the Black population was of little importance. The crude racialism that walled American culture exacted a toll that only the most desperately alienated at the racial and psychological margins of the Black and white societies could be expected to pay. — Cedric J. Robinson, Black Marxism_ The Making of the Black…, 1433