History furnishes us with innumerable instances that prove this law. It shows, with a startling clarity, that whenever Aryans have mingled their blood with that of an inferior race the result has been the downfall of the people who were the standard-bearers of a higher culture. In North America, where the population is prevalently Teutonic, and where those elements intermingled with the inferior race only to a very small degree, we have a quality of mankind and a civilization which are different from those of Central and South America. In these latter countries the immigrants–who mainly belonged to the Latin races–mated with the aborigines, sometimes to a very large extent indeed. In this case we have a clear and decisive example of the effect produced by the mixture of races. But in North America the Teutonic element, which has kept its racial stock pure and did not mix it with any other racial stock, has come to dominate the American Continent and will remain master of it as long as that element does not fall a victim to the habit of adulterating its blood.

https://gutenberg.net.au/ebooks02/0200601.txt - Main Kampf

The confederate states and their Jim Crow policies inspired Hitler. and black GIs came home from liberating Europe to be lynched for being "uppity".