None of the four sectors you mention: agriculture, manufacturing, construction, and war is more diverse than 90 years ago. They are all dominated by multinational monopolies, as well as the other, newer sectors you list.

Add on top that all sectors have outsourced as much as possible the last 30 years (thanks, Bill!).

US infrastructure is falling apart. Most of it dates to the great depression, and is woefully under maintained.

This combines to make the US system very fragile. See what happened during Covid and then afterward with shipping for a smaller example.