iPhone displays are most definitely made in South Korea. Some of the components are made in Japan as well, not much is made in the USA beyond the software stack (which you are also most definitely paying for since SWEs aren’t cheap!). Also iPhones are made in SEZs (none of the components are tariffed in these zones), so they are tariffed when imported into China.

I doubt Trump tariffs will be based on value add. It would be a logistical nightmare, and he doesn’t strike me as someone who thinks too deeply about these things.