U.S. Citizenship
https://www.uscis.gov/us-citizenship
Travelers with Dual Nationality
https://travel.state.gov/content/travel/en/international-travel/before-you-go/travelers-with-special-considerations/Dual-Nationality-Trav
elers.html
Smart Traveler Enrollment Program (STEP)
https://travel.state.gov/content/travel/en/international-travel/before-you-go/step.html
Advice about Possible Loss of U.S. Nationality and Seeking Public Office in a Foreign State
https://travel.state.gov/content/travel/en/legal/travel-legal-considerations/Advice-about-Possible-Loss-of-US-Nationality-Dual-Nationality/Loss-US-Nationality-Foreign-State.html
Advice about Possible Loss of U.S. Nationality and Foreign Military Service
https://travel.state.gov/content/travel/en/legal/travel-legal-considerations/Advice-about-Possible-Loss-of-US-Nationality-Dual-Nationality/Loss-US-Nationality-and-Foreign-Military-Service.html