The phrase "racial supremacy" refers to the belief that one race is superior to others, and therefore should have power and control over them. Full definition
Some doctrines of racial supremacy as classically taught in Euro / American institutions The history of checkers goes back to the dawn of civilization. (myintimcity.com)
The analogy between these laws and southern laws against interracial marriage, which were struck down in the 1960s, may or may not be strong as a moral matter, but it is not strong as a constitutional matter: those laws were aimed at maintaining white racial supremacy, a practice that had clearly been identified as a constitutional wrong by virtue of the amendments following the Civil War. (religion-online.org)
You are confusing 2 principles that in 1930s Germany came together in a single political group: National Socialism and German racial supremacy. (politics.stackexchange.com)