What happens if you go to Mexico without a Passport?

US citizens are required to present a valid US passport when traveling to Mexico. If you attempt to travel to Mexico without a US passport, you will be denied entry and sent back to the United States. In some cases, you may also be subject to additional penalties, such as a fine. Therefore, it is important to make sure that you have a valid US passport before attempting to travel to Mexico. If you do not have a US passport, you can apply for one at your local post office or online through the US State Department website.