There might be differences between the Shanghai and California factories that muddy the comparison:

- California factory was made in previous Toyota/GM factory, not sure how much of it is completely optimized compared to Shanghai factory

- Shanghai factory is built much more recently (2010 vs 2019)

- California factory also makes low-volume S and X vehicles in addition to 3 and Y

- California (especially the area around the Tesla factory) is not representative of most US auto manufacturing, most companies including Tesla have factories in other US states