>but selling outside the US would mean importing parts into the US and exporting computers outside, paying tradewar-level tariffs both ways

exactly. This is why it doesn't make much sense to setup a US shop as it will be for US market only. The product produced in a US shop would still cost even for domestic market at least like "imported plus tariff" and with no ability to export it. There is a reason Russian cars are complete crap and aren't exported. That reason is called tariffs.