Exactly. If my partner and I make $200K / year, we can live comfortably in most places in the US. If we have eight children to support on that $200K / year, we would struggle: the rent increase alone would be ruinous, not to mention food, clothing, and medical costs.

For the US to have GDP per capita similar to China, the US population would have to swell to more than 1.5B people - five times its current population.