The reason the iPhone is made in China is because, well, there is no U.S. manufacturer of most of the electronic components used. And there is no U.S. manufacturer because, well, American workers expect a living wage, insurance, and retirement. The U.S. Government expects EPA environmental control which costs money to comply with (no regulations in China -- none at all. You can dump whatever you want into the rivers, literally). And there are no exorbitant taxes in China like in the U.S. So, goodbye American manufacturing. Nice knowing ya.
As for Apple, they do not make their own components, except in rare cases. The processor itself is (I believe) made by Samsung (Korea). That's why Steve Jobs was afraid of suing Samsung (as he threatened) for "ripping off" the Iphone with some of their Android models. Why? Because his own iPhone has Samsung hardware in it. It would be kind of a conflict of interest if he sued the company that made his phone work.
Apple nowadays (unlike the 80's) just designs products and sends the blueprints to Korea and China for manufacture. There's only a few chip fab plants in the world, and most of them are in Asia (I believe Intel has one in Britain and in the USA). AMD has most all of theirs in Asia, which is why they are less expensive than Intel.
Even though the Iphone is made primarily in China with components made in other parts of Asia, it is still way expensive. This is why, I think, most people use Android.