The racial and ethnic diversity of a state is an unreliable predictor of the political party tendency the state. You see this when comparing the Diversity Index to the state’s politics.
The Census has developed the Diversity Index: A value of 0 indicates that everyone in the population has the same racial and ethnic characteristics. A value close to 1 indicates that almost everyone in the population has different racial and ethnic characteristics. We have converted the probabilities into percentages to make them easier to interpret.
For example, in 2020 there was a 73.7% chance in Prince William County, Virginia, that two people chosen at random were from different racial or ethnic groups. In Hawaii County, Hawaii, there was a 77.7% chance that two people chosen at random were from different racial or ethnic groups.
For the entire country, the chance that two people chosen at random will be from different racial or ethnic groups has increased to 61.1% in 2020 (That is, a DI of 61%) from 54.9% in 2010.
In 2020, Republicans totally dominated in 15 states. Lowest diversity was Wyoming at 32%. The highest diversity was Texas at 67%
Democrats totally swept 14 states. Lowest diversity was in Colorado at 52%; highest. Highest diversity is Hawaii at 76%.
Diversity is the long game in the U.S. reflecting slave ownership, 1880-1910 immigration, and immigration since 1970. Politics is a shorter game. Hence, Northern New England states, which send only Dems to Congress, have an average index of 20%; Great Plains states of 38%, and Deep South of 55%.
Political profiles from here, and Census figures from here and here. Also go here.