The reason why iPads are built in China is because of a thing called Comparative Advantage [1].
Even though the US could reasonably produce iPads _more_ efficiently than China, it doesn't. The reason is that the US is even more efficient at supplying higher-cost services (software, finance, etc.) than China that it would be at producing iPads. Therefore, the US is better off training more of its workforce for higher-cost services than to train them to be laborers.