FX cost basis calculator →US estate tax exposure →
Your broker reports the price move. Your tax office taxes the price move and the exchange-rate move together. How the two separate, which rate applies where, and why a loss can still be taxed.
A non-US citizen holding US stocks or US-domiciled ETFs is exposed to US estate tax above $60,000 — regardless of where the broker sits. What counts, what it costs, and what Irish UCITS change.