Passport and visa requirements to leave the United States will vary depending on which country you are visiting. To be able to get back to the U.S., however, you need a U.S. passport or passport card. As of 2007 the passport requirements for U.S. citizens have changed as part of the U.S. Western Hemisphere Travel Initiative, which has been implemented to improve border security. Before 2007 U.S. citizens only needed to supply birth certificates and photo IDs to enter Canada, Mexico and other countries, but passports are required for all of these now.
Passport cards are accepted for travel between the U.S., Canada, Mexico, Bermuda and the Caribbean area. The passport card is cheaper than a regular passport book, and has been designed to increase speed and efficiency at United States land and sea border crossings. Passport cards contain a vicinity-read radio frequency identification chip (RFID), which indicates a stored record in government databases. Customs and border protection inspectors are now able to access photos and other information stored in the database.
U.S. passport books are required to travel internationally. If you are a first time applicant, you need to apply for the passport in person at a passport agency or an acceptance facility (see references for a link). You will be required to submit proof of U.S. citizenship in the form of one of the following: a certified U.S. birth certificate, a Consular Report of Birth Abroad or Certification of Birth, a Naturalization Certificate or a Certificate of Citizenship. If you want to renew your passport, you can submit the forms with your current, undamaged passport by mail.
Visas and Other Requirements
Visas and inoculations are required by many countries if you are traveling abroad. The requirements for application vary greatly. For some countries you need to be vaccinated against a number of diseases and undergo a medical examination. Apply for a visa at the nearest embassy of the country you are visiting. Some countries, like Australia, allow online visa application for U.S. Citizens.
The travel.state.gov website supplies information on the requirements for most international countries (see references).
Children under 16
An U.S. or Canadian citizen child under the age of 16 traveling between Canada, U.S., Mexico, Bermuda or the Caribbean needs to provide an original copy of his birth certificate, a Naturalization Certificate, a Canadian Citizenship card, a Consular Report of Birth Abroad or a U.S. Passport Card. All children traveling internationally by air need to present their own passports. When applying for a passport, a child has to apply in person with both his parents present.