There is some evidence (p25) that economic inequality isn't correlated with economic system; specifically, that the share of income going to the poorest 10% is uncorrelated with economic freedom. As Friedman put it, the pay multiple between boss and worker in the USA and USSR were the same; the difference was that the American boss could only fire you, whereas under communism, you could be shot.

Secondly, comparing the wealth of Americans with the residents of chad is a bit tangential, unless all live under one economic system. If Chat doesn't operate in the same system as America, the same comparison could simply be evidence for the superiority of the American system. The inequality within America is a more relevant piece of information here.