Here's my estimate, taken mostly from figures from Apple's 2024 annual report (as reported by Gemini Flash).
Apple's total worldwide revenue for fiscal year 2024 was $391.035 billion. The Americas Segment (which includes the US) represented $167.05 billion of that, leaving $224 billion for the rest of the world.
Apple reports that their cost of goods sold was $210.352 billion, leaving 180.68 billion as so-called "gross profit". The majority of this gross profit will be used to pay salaries and other expenses (e.g., office space) of having employees, most of which goes to Americans. (Most of the rest will be "retained earnings", which means it either goes back to investors or is used to try to generate new streams of revenue.)
But only some of that gross profit will come from exports. Let's assume that exports are as profitable (per unit of revenue) as US sales are, which seems reasonable to me because competition (mostly from Android) would be the main thing keeping gross profit low, and Android is a major competitive force in the US market, so estimated gross profit derived from sales to the rest of the world would be 180.68 * (224 / 391.035) == $103.5 billion. That is revenue from all products and services, and Apple reports that revenue from the iPhone is 0.5145 of all revenue (worldwide) or about $53 billion per year flowing from the rest of the world to Apple (and to governments in the US in the form of taxes).
To be clear, that's assuming that zero of the hardware (more precisely, zero of what accountants call the "variable cost") that goes into an iPhone is bought from US suppliers (which seems a reasonable assumption to me).
