[cossatot]

While I partially agree with your assessment, it's worth noting that much of the dynamic settlement of the US has been based on commodity booms, which really can't be considered perpetual parts of the economy. People had to leave their homes to go clear the prairie, log virtually all of the US forest, mine the West Virginia coal and then the Wyoming coal after that, etc. Once those resources are used up, there is little left for people to do, regardless of technological advances that require fewer workers for the same output, much less trade deals (how much wood and grain do we import?). The economies oriented around renewable resources (Oregon timber for example) simply can't sustain as many people because the environment can't continually produce the output that it did during the initial exploitation.

This of course affects the downstream, more industrial elements concentrated in cities as well, which process the ore and lumber and make engines and furniture.