This is a good example of what the social-science methodologists call “interaction effects.”
Non-white and Latino Southerners are no less likely to get the right answer than are non-whites and Latinos in the rest of the country. So it can’t be something in the water, or the effects of the fried-meat-white-bread-and-boiled-veggies culinary culture of the South.
And whites in the rest of the country also do fairly well on the question. So it can’t be evidence of a cognitive deficit correlated with melanin and carotene deficiency.
But somehow the interaction of whiteness and Southerness produces deep and abiding ignorance. Perhaps it’s Vitamin D poisoning due to the effects of intensive exposure to sunlight among people with little capacity to tan. Or just the effect of seeing a member of the despised under-caste elevated to the Presidency, and grossly outperforming his white Southern predecessor.
Yes, you could draw the inference that the white South lacks the basic pre-requisites for successful democratic self-government. Perhaps, from a strictly pragmatic viewpoint, a period of guided democracy, under the tutelage of more culturally advanced guides, might protect the white South from the inevitable disasters that occur when the demands of democracy are imposed too suddenly on backward peoples. But my faith in democracy is stronger than that, and the Constitution provides for no such trusteeship option.
All we can do is to provide as much support from the outside as we can for the sane minority of the white South, and of course make sure that their insane brethren are never allowed to influence national policy in any way.