According to FBI hate crime statics regarding reported incidents of racially motivated hate crimes perpetrated in 2017, there were 2,013 reported incidents of anti-African American hate crimes, 427 reported incidents of anti-Hispanic hate crimes, 102 reported incidents of anti-Arab hate crimes, 938 reported incidents of anti-Jew hate crimes, and 273 incidents of anti-Islamic hate crimes.
This means, supposing there is one individual white supremacist for each racially motivated hate crime perpetrated each year, there'd be fewer than 4,000 White Supremacists out of 300 million persons in America. Hence, 99.998 percent of the population are not white supremacists.
In conclusion, white supremacist are a statistically insignificant portion of the U.S. population.