The book Why Nations Fail: The Origins of Power, Prosperity, and Poverty neatly summarizes why nations fail in a few lines:

(A nation) is poor precisely because it has been ruled by a narrow elite that has organized society for their own benefit at the expense of the vast mass of people. Political power has been narrowly concentrated, and has been used to create great wealth for those who possess it.

Sound like any countries you know? Perhaps we should flip this question around and ask: how many nations don't fit this profile?

I submit that this dynamic of failure--the concentrated power and wealth of self-serving elites-- is scale-invariant, meaning that it is equally true of communities, towns, cities, states, nations and empires alike: all fail when they're run for the benefit of a narrow elite.

There is a bitter irony in the ease with which American pundits discern this dynamic in developing-world kleptocracies while ignoring the same dynamic in America. One would imagine it would be easier to see the elites-inevitably-cause-failure in one's home country, but the pundits by and large are members of the Clerisy Upper Caste, well-paid functionaries, apparatchiks, lackeys, factotums, toadies, sycophants and apologists for the very elites that are leading America down the path of systemic failure as the ontological consequence of their self-serving consolidation of wealth and power.

For those who doubt that America is ruled by a narrow elite: I don't have charts for standard-issue third-world kleptocracies, but I doubt the concentration of wealth and political power is much more extreme than in America:

In a simulacrum democracy where the highest bidders control the state, who do you think can readily buy political power?

And the policies of the elites have really spread the prosperity around in the past few years (sarcasm-off):

What's truly interesting about the authors' exhaustive survey of the inevitability of failure in elite-dominated nations is how cities dominated by narrow elites fail, states controlled by narrow elites fail, and indeed, any organization that serves the interests of a few at the expense of the many fails for the same reasons.