Of course they could make their products in the US.
But are you as a consumer willing to pay 4, 5, 10 times as much for those products in the name of domestic industrial welfare?
No you are not, and neither is anyone else. Following your advice would be the end of aapl.
I doubt that the cost would be much more than 30-50% higher. But, 30-50% higher on top of the premium prices would certainly kill some sales. $800 for an iPhone is bad enough, but imagine $1000-1200 for one made in the US? And they would not generate more profit!