Benjamin Hale sum up why it is Americans end up voting for policies that actually thwart their interests: they make decisions about justice according to a "veil of opulence," the opposite of the "veil of ignorance" advocated by Rawls:
Those who don the veil of opulence may imagine themselves to be fantastically wealthy movie stars or extremely successful business entrepreneurs. They vote and set policies according to this fantasy.
But the veil of opulence operates only under the guise of fairness. It is rather a distortion of fairness, by virtue of the partiality that it smuggles in. It asks not whether a policy is fair given the huge range of advantages or hardships the universe might throw at a person but rather whether it is fair that a very fortunate person should shoulder the burdens of others. That is, the veil of opulence insists that people imagine that resources and opportunities and talents are freely available to all, that such goods are widely abundant, that there is no element of randomness or chance that may negatively impact those who struggle to succeed but sadly fail through no fault of their own. It blankets off the obstacles that impede the road to success. It turns a blind eye to the adversity that some people, let’s face it, are born into. By insisting that we consider public policy from the perspective of the most-advantaged, the veil of opulence obscures the vagaries of brute luck.
This is the philosophical answer to the question asked by Thomas Frank in What's the Matter with Kansas.