You're confusing claiming dual nationality, which the US has no problem with, with entering on a non-US passport as a US citizen, which is not allowed. Your rel

You're confusing claiming dual nationality, which the US has no problem with, with entering on a non-US passport as a US citizen, which is not allowed. Your relative was lucky that the immigration officer allowed that. "U.S. nationals, including dual nationals, must use a U.S. passport to enter and leave the United States." https://travel.state.gov/content/travel/en/legal/travel-legal-considerations/Advice-about-Possible-Loss-of-US-Nationality-Dual-Nationality/Dual-Nationality.html https://travel.state.gov/content/travel/en/legal/travel-lega...