While having every single component of the iPhone being manufactured in the US (something along the lines of RCA pre-1970) is indeed pure fantasy. You could hypothetically assemble the iPhone in the US, with many of the components being locally produced.
But for that, you would need a competitive smartphone market (i.e. no 35% margin for Apple, they would have to deal with 2%-3% profit margin, 5% tops) and Americans consumers would have to be exposed to the true cost of the device. No annual upgrades through your carrier. You pay $1,500+ for a baseline iPhone and you expect it to last for ~5 years with occasional repair.