American citizens require passports to exit and enter the US and all other countries in the world. It is required that you carry the correct identification while traveling abroad. You will need a passport to travel every time you leave the United States or its territories. There is one exception to this rule for American citizens, traveling by land or sea to Canada, Mexico, the Caribbean, and Bermuda - a passport card can be used, it is also possible to only apply for a passport card and not a passport book.