A supply chain that also comes from Shenzhen... last time I checked, North America doesn't make chips or other components either.
That's never been true (at least since the first chips or components). A lot of my Shenzhen orders have to wait on international airfreight on US-made chips because the ones I spec'd (basically the only ones that would do the job) are US-manufactured and warehoused.
Recommend you look at a world map of Intel fabs. Or Micron Fabs.
Basically anything aerospace and defense related will care more about speed and compliance than cost.