As I said in my last post, Donald Trump did better than Mitt Romney had in states with few "minorities" (blacks or Hispanics) and worse in states with large numbers of "minorities." I have read a lot of articles about the 2016 election, but don't recall anyone noticing this. In a post from December 2016 I noted that some of Trump's biggest gains took place in states with few minorities, but I didn't follow up on it. Here is a figure showing gain or loss over 2016 by percent black or Hispanic. The correlation is about 0.5 for all states and 0.7 if you exclude Utah. I don't think that it's likely to go away if you control for other factors, so how should it be explained?
One popular analysis of the 2016 election was that it was about the defense of "whiteness," which is a mixture of prejudice and the rational (although selfish) defense of group interests. People who advocate this don't pay much attention to regional differences--they generally focus on making a case that there's a historical pattern of white backlash after every move towards racial equality. But it seems that this account implies regional differences too. Racial interests will make more difference to white voters if the percentage of racial minorities is larger: that is, minorities will be more of a threat where they are more numerous. To the extent that Trump appealed to "whiteness," he should have gained more where the percentage of minorities was higher. That is the opposite of what happened.* So how can this pattern be explained? The assumption of the usual account is that an appeal to "whiteness" will gain votes among whites. But white opinions on race have changed a lot over time. The decline in straightforward prejudice is well known, but whites have also seem to have become less likely to think that they are the ones who are discriminated against. That suggests that an increasing number of whites will have a negative reaction to a "defense of whiteness" appeal--they will regard it as unfair. Even whites in the middle--those who don't think there's much discrimination against either blacks or whites--may have a negative reaction because they think it will increase racial conflict.
So my view is that to the extent that Trump appealed to "whiteness," that hurt him in much of the country. The thing that helped him was an appeal to nationalism, as discussed in this post, among others.
*Another variant of this analysis is that Trump was no different from Romney, Bush, etc.: they all appealed to "whiteness" and he was just cruder. But this would imply no relationship.