My guess as why many "US" manufacturers are located in California mostly has to do with the import/export market and access to the ports in San Diego, L.A., and such. I think it has little to do with where people actually dive. I would further guess that due to the trade imbalance, many ships leave here with much less than they came with. That should (in economic theory...) reduce the shipping cost of exports. I think they would try to recoup as much of their cost for the return journey rather than come home with an empty ship. And we won't even begin to factor in fuel cost to send an empty ship across the ocean... As for the companies that do outsource their manufacturing to China, Taiwan, South Korea, Singapore, Malaysia, etc., It cost very little to have your ISO container delivered to a local warehouse. To steal a line from the real estate folks, location, location, location.
This irritating economics lecture was brought to you by the letter "E"