I think it's not unusual for companies to be forced to accept such risks if their competitors have already done so and that's enabling the competitors to win.

Governments can intervene to keep the playing field level, while protecting the national interests.

If it's true that the US has a dominant position in this space, then it's true that the US government has an opportunity to prevent the US companies from shifting manufacturing to where it's likely to result in IP theft in the process of competing with eachother in the manufacturing costs deparment.

If all the companies in the space are forced to ignore the cheaper manufacturing option, that self-destructive avenue of competition is off the table on equal terms. However there's still the threat of foreign competition undercutting on manufacturing, if they catch up in the IP department (which IP theft certainly accelerates).

This makes sense... So IIUC, it's not clear whether government restrictions are a net positive or negative for the US economy: it helps against one source of IP theft, but hurts in the sense of lower global competitiveness due to higher manufacturing costs.

A very difficult trade-off I guess.

IANAL but I believe the US government considers access to superior Silicon a matter of national security and regulates it as such.

It made a crucial difference in the 1980s but now? Who cares if your CPU is a couple of generations old?

It's more expensive to manufacture the same amount of compute power using older processes. That makes old silicon not competitive. From the viewpoint of the consumer, indeed, price per compute power is relatively constant, but from the viewpoint of a silicon manufacturer, newer processes are cheaper per compute power.

This doesn’t answer the parent point. Compute is more expensive with older tech, so what? They’ll just pay more. Consider North Korea. Their ICBM technology is pretty bad compared to the state of an art, however it is still great security concern.

They won't sell, and not enough to fund competing research. I'm pretty sure the security concern isn't directly related to defense, but to the security of US industries and economy.