You are right, there aren't much farmers left in usa, I guess less than one percent of population whose prime source of income is farming because most farmers in usa has other non-farm-related sources of income too.

But usa is just a minute part of world on any perimeter except fossil-fuel-driven-economy and fossil-fuel-driven-technology. Most of the world still live in villages, a simple low-bio-foot-print life and has community-sense that americans don't.

Its right that babylon, rome, athens, tenochtitlan, constantinople were and are all cities but only a minute part of population lived in those cities as compared to populations of whole civilizations of each of these countries. Also don't forget that we can build sustainable cities but it has to be much much low-energy-consumer than modern cities, a scaling down of 100 i should say.