Just because the US doesn't manufacture anything anymore, doesn't mean you couldn't do it very successfully even with 'high' labor costs. Ever been to Germany?
Well this is the point. It's not the cost labour but the cost of the engineering support to keep the whole chain running.
Apple could manufacture in US with robotic factories to balance the labour cost but if they can't get the resources they need to keep those factories running then they aren't going to do it.
The countries that manufacture today have all favored their technical education systems.