The Nazis vs Americans solo, meaning the nazis did not first invade other countries and get bombed by those countries, instead just coordinated an attack against the United States only, I believe they would have stood a fair chance. Or ‘fair’.
The reasoning is because german technology was way better than American , their planes, tanks, armed vehicles.
America had more soldiers by about maybe 3 million, Germany having approx 9m and America approx 12m. But considering how advanced their technology was Germany would have stood a more even chance against the Americans.
As for the question in hand, the belief of Hitler, who controlled and led the nazis, was that anyone not white and/or Jewish was not a person.
They incarcerated, ‘sterilised’ and discriminated against the blacks. I believe the outcome for racism in America would be much worse with Hitler in charge. They also denied statehood to black people.