That’s not entirely clear. Certainly even in the US it’s more “efficient” if tech were anywhere but SF, but that’s not the case. Trade happens when countries agree to it, according to local taxes imposed, etc. China and Mexico did not have the manufacturing might they do now before trade deals allowed that flow, combined with a cultural trend in management to “outsource” everything and local in China and Mexico strategy to be that source (by doing things like heavily subsidizing energy, shipping, etc.)