Apple has enough money that they could fire up their own fab plants and make everything they need inhouse.
But that'd be expensive. Really expensive. Apple would have to buy up tons of space to build a loads of multibillion dollar factories to produce the devices, and hire hundreds of thousands of people to turn them out quickly and efficiently. Apple would become a bloated, unweildy company in the process, no longer singly focused on just making nice consumer products, and the only way they'd be able to maintain their profit margins would be to double or triple the price of everything they sell.
In the end, they'd end up draining their bank account without any substantial returns on their investment, and would probably be worse off, considering they don't have the experience to produce panels and chips en masse efficiently like Samsung or even LG does.
I'd believe this and be all over it in agreement if Apple didn't recently spend $100 Million on a US based manufacturing facility to produce their MacPros. Yes, I'm comparing a $650+ device to a $3,000+ device simply because Apple and many other manufacturers have found many ways to streamline the production of tech devices with robots which only require humans to assemble fewer parts. Bringing production of EVERY Apple product to the US is possible and would benefit this poor country so much but in the end, why would a company want to spend $XXXXX amount of dollars producing devices in American when they can do it all for only $XXX in China?