Right-wing media has been force feeding resentment and victim mentality to working class whites for decades, distracting them from their own exploitation by richer whites by pointing to blacks and immigrants, painting them as lazy, violent, criminal parasites. So while these white workers are breaking their backs to give their bosses higher profits, they blame their real struggles on those less fortunate than themselves. And as a result they refuse to accept that others suffer even more than they do, and fail to unite with those minorities with which they actually have more in common with than the plutocrats they identify with and dream of becoming.
Basically, white supremacy is a con to keep workers and the poor divided and conquered.