May I suggest that you add to your research of this question my own musings:https://medium.com/age-of-awareness/white-backlash-has-already-begun-660fea4d1224

Also, the historian extraordinaire, Dr. Gerald Horne of the University of Houston, has deeply researched and expounded upon the whole matter of the "when" and "why" white supremacy/white racism in the US began. Dr. Horne has written many books, but two of the most notable are: "The Counter-Revolution of 1776 -- Slave Resistance and the Origins of the United States of America" (2014); and "The Roots of Slavery, White Supremacy, and Capitalism in Seventeenth Century North America and the Caribbean" (2017).