One obvious problem for 21st-century America: the seeming zero-sum paralysis of our national-level governing system, illustrated most recently by the spectacle of the Congressional-Executive / Republican-Democratic tussling over the Iran negotiations.
Another obvious problem: the seeming polarization of American society on almost every axis, from economic well-being to political and cultural beliefs.
We tend to discuss these problems as if they are serious but only indirectly connected. That indirect link would be via the increasing Citizens United-era dominance of big money in politics. This, in turn, makes it harder even to consider, let alone enact, policies that would blunt the winner-take-all aspects of a globalizing economy or rebuild the public institutions that have historically buoyed a middle class and protected the poor.
One specific virtue of an admirable-on-many-fronts review article by Jill Lepore in the latest New Yorker is that she makes clear the connection between these twin pathologies. This argument comes in a discussion in her piece "Richer and Poorer," which begins with a discussion of Robert Putnam's new book Our Kids and ends with material from a forthcoming book called Inequality: What Can Be Done?, by Anthony Atkinson.