On top of that: not all countries are the same size. Why should Luxembourg be autarkic but Cleveland should not be? You're completely right that "country" is an arbitrary level to say "autarky is ok at this level."

Why do you think? National boundaries tend to be relatively homogeneous in terms of human development, which prevents corporations from engaging in labor arbitrage. Comparative advantage is beneficial in capital terms only, and harmful if it is used as a means to deny people basic human dignity in their working conditions. It enables for as wide of a market as possible without labor arbitrage.

The US is nowhere near homogeneous. At best, it's bimodal (coastal megacities vs. interior). There are labor arbitrage opportunities of more than 2x between i.e. Mississippi and DC [0]. Discussions about Silicon Valley's housing crisis routinely beg tech companies to engage in labor arbitrage by opening satellite offices or permitting remote workers in cheaper parts of the country.

The chasm between human development in a country's cities vs. its countryside is even wider around the world.

[0] https://en.wikipedia.org/wiki/List_of_U.S._states_by_income

>The US is nowhere near homogeneous.

Ah yes, that would be the definition of relatively.

Or are you implying that the difference in development between SF and Mobile, AL is bigger than the difference between the United States and Bangladesh? Because I would be highly suspect of that implication...