We couldn't make an iPhone because apple would refuse to cooperate, not because of a technical limitation. We could make a similarly capable phone though.
Apple’s putative refusal to cooperate is surely not the only barrier here. I doubt U.S. consumers would pay a premium for a U.S. iPhone whether Apple thought it wise or not. But when the U.S. president’s branded Made in America phone comes out later this year I guess we’ll see. I’m sure the release is just around the corner.
If the tariffs are high enough there won't be a premium. It also solves the deficit spending problem which needs to happen since no one seems to be able to handle the idea of any spending cuts.
I can almost imagine we would have more trouble getting domestic phone screens, but I'm not doing any research to validate that gut feeling.
I think the biggest problem would be whether we could automate assembly enough to avoid having high labor costs on each unit