Opinion without knowledge is prejudice. Prejudice in areas of race is racism. Opinion without knowledge in areas of race is racism. The US was founded on racism and our founding document, the US Constitution, is tainted with racism. Counting slaves as 3/5 person is racist, pure and simple. The amendments to the Constitution have lessened the taint, but not eliminated it.
We know that parts of the US are more racist than others, and those areas tend to vote Republican. Not all Republicans are racists, but racists, if they vote, tend to vote GOP. Hillary Clinton was wrong to claim that half of Trump supporters are deplorable. The number of deplorable and racist Trump supporters is unknowable. Probably there are some and there may be many, more than half or less than half, but still unknowable.
Racism within the US is the rock, fatal flaw, that could sink the ship of state which is the US republic. To combat racism within the US, I recommend consciousness raising and deliberate attempts at greater empathy for our fellow-men. The US is only one ship and we survive or sink together.