>We live in a society that couldn't rebuild, if it had to, the New York City subway, or the Interstate Highway System, or the national electric grid, or numerous other features of industrialized 20th century America.
We live in a society which lacks the collective will to do such things. It's only after the knowledge required to do so is lost that it can't be done again.
Unlike after the fall of Rome, there are machine tools all over this country that make it possible. We don't have to rely on manpower, or beasts to do the work. Sitting in basements, garages, barns, forests. We've got the natural resources. We also have a widely distributed archive of machinists books, literacy, and the hacker ethos on our side.
Mostly it's the financial distortions of the price of money, and tax policy, that have moved our manufacturing offshore, for now.