You'll need to provide a certified copy of your birth certificate and passport photos. Once the application process is complete, you should receive your passport in about six weeks. If you've had a passport and it has expired within the last 12 years, you may simply renew it. To do so, you'll need to complete a new application, provide new passport photos and your old passport if possible. If your passport expired more than 12 years ago, you'll have to apply for a new passport.
Few countries require the same documentation to enter their borders.
While some countries require no citizenship documentation at all, many require even more than a simple passport. For example, a passport is not required to enter many countries in North, South and Central America. But even if the country you're visiting does not require a passport to enter the country, be prepared to provide some proof of U.S. citizenship upon your return to the United States. This type of proof may include a birth certificate, certificate of naturalization, or even an expired passport. According to U.S. Customs officials, a drivers license proves only that you can drive, not that you're a citizen of the United States.