This is the result of the long-standing complicated issue with race in the U.S. I wish it was something more profound but it's not. Race has always been the biggest political issue in this country - sometimes overt, sometimes subtle but always the catalyst.
1) We struggled with race when assigning Congressional seats to states. It shaped early voting. By not giving the South full count for their slaves (3/5), they had less voting power relative to their population. It and slavery in the territorial expansion eventually led to the Civil War.
2) The issues surrounding slavery eventually led to the Civil War. A massive war that created a still existing divide in how America self-identifies. The aftermath of the Civil War and Reconstruction policies that attempted to maintain slave-like conditions vs. the fight for integration led to years of legal and constitutional changes that culminated in the Civil Rights Act.
3) The results of the Civil Rights Act created the groundwork for the aggrieved anti-integration voting bloc that the GOP manipulated for political gain. A voting bloc whose influence outweighed their numerical value as time went on. But a group that was primed to be unsupportive of the first minority president.
4) The first minority president that basically represented the culmination of the centuries of fearmongering that is rooted in the anti-abolition arguments of the 17th and 18th century. That 17th and 18th century argument was that the white man is superior and it's natural for him to have dominance over other men. 200+ years after the first arguments over how to treat blacks in the political process, those people who's forebearers who fought their inclusion are living in the very world they wanted to prevent.
This issue, race, is the driving force of our political arguments. Sure, we get offshoots but they always come back to this. Welfare, for example, is an issue that is superficially not about race but the arguments for and against it, almost always descend into debates on racial groups use. Public education should be a race neutral topic but, no matter how one tries to keep the topic on the value of educating our poorest kids, it inevitably turns into a commentary on race.
Does HRC or Trump solve either of those things? Nope. Frankly, no President can. So long as some Americans continue to evaluate the value of political policy on the grounds of racial impact it will remain so. I want to draw a distinction between political policy and social policy. Putting more minorities on tv shows is social policy. What happens on Twitter is social policy. BLM is social. These are not political, they are not legislation. No politician will ever vote on them. They are not what I'm talking about.