https://www.kut.org/post/one-reason-apples-computers-are-mos...
https://www.nytimes.com/2019/01/28/technology/iphones-apple-...
Basically, the US simply does not have the infrastructure to manufacture complex items in mass quantities. We haven't invested in that infrastructure, whereas China has, so they have the ability to do this stuff, and we don't. So trying to build an iPhone in America is like trying to build an iPhone in Zimbabwe or Sudan or Armenia: the infrastructure simply doesn't exist and it isn't feasible to take on a project like that there.
America stopped being an industrial powerhouse decades ago, by choice, and you can't just bring that back overnight, especially when some other countries never gave that up and will easily out-compete you.
The US doesn't manufacture those items because it has no capability to do so.
There are no factories, no supply chain, no expertise and no known how.
There are some things that are cheaper to manufacture in US, (surprise!) if you manufacture for the local market, than in China, but them being simply cheaper still doesn't mean you can actually manufacture them.
I myself tried to setup an electric scooter factory, first in Canada, and than in Washington state. We were simply unable to find even moderately competent manufacturing engineers, nor the line workforce.
Of course, every consumable and every part had to be imported.
And both of the above meant that we decided to close the business in under 6 months.