If I were to have to speculate about how our extremely successful and wealthy country could choose to fail to meet the modest, minimum requirements for rational and effective self-government I would say that it's because of an undercurrent of fear and that this fear is rooted in disunity over race.
We can't behave because we are divided. White people don't identify with or accept the legitimacy and rightful existence of black people and, to a lesser extent, Hispanics, because they see them as more like themselves in their circumstances than they are and so less like them as people.
White people want to relate to black people on the basis of their own irrelevant experience, in other words. For generations blacks lived under a racist, terrorist, totalitarian, extremist religious regime, a substate of America called Dixie. And whitey wonders why black people are different.
Black people and white people are less alike circumstantially and more alike existentially than white people think. It makes sense from within black culture but white people can't go there. They don't understand what it's like to be black. They can't but there is such a thing as empathy.
And it's possible to live with an eye to justice and fair-play and decency instead of giving up. This is a problem of segregation, the lack of intimacy between racial groups, because it makes empathy and understanding impossible. It's getting worse with us as income and wealth disparity increase.
But poorer white people are as disenfranchised as black people now and coughing-up totalitarian leaders, to their own detriment, like the sputum of Trump. It's only a sign of frustration and confusion. The ones behind it were also responsible for the terrorist substate, which they want to see reborn.