I don’t think homogeneity has any relationship to “best governed” or “worst governed”. Norway’s pretty homogenous and AFAIK its doing well. Mexico’s pretty homogeneous and it seems like kind of a shithole. I would not think any direct relationship exists. It has a relationship to “how easy is it to convince most to agree” which is completely different. Discrete groups of people can agree on great ideas or terrible ones. Speed of agreement does not = merit of results. A greater variety of competing ideas means more ideas to choose from, which may result over time in better ideas being picked, but it also mean slower widespread adoption of any particular idea.
Serious question: do you think a state which uses a rule of law to come to policies you don’t agree with is badly governed? Is Texas a badly governed state because its citizens have largely agreed on abstinence-only sex education, one of the worst ideas of all time in terms of results? Is there something lacking in Texas’s rule of law that permitted these ideas? I say no. Texas’s observance of the rule of law, their use of representational democracy as opposed to say, dictatorial fiat, is healthy to my knowledge. Texans just think differently for a whole host of reasons and so they come to different conclusions about what the “best” solution to sexual education is.
And Texans can think those thoughts and live in Texas, and I can think different thoughts and live in NYC, and we both agree we each have equal right to voice our thoughts, and an equal right to persuade others to our view, and in the meantime we’ll argue about it, and that what makes us all Americans. And maybe someday, or not, the entire country will reach a consensus.