Why did Americans (U.S.) go from being extremely racist to a extremely tolerant people?

Have we really become a "saint compared to the past"? Eugenics movements was heavily instilled in the United States through out the 20th century. Yes, we have partnered on global issues but I disagree with your statement of defending rights of people. We should have listened to the advice of dear old Washington and not interfere with others. Instead, we go out and demand to help other nations who don't want us there. We play nice to our not so friendly countries(China and Russia) who supply weapons to other nations such as Iran and Sudan. Our actions might be different. But they are still underlined with the same motive