You can't go to Mexico without a passport either. You can't come back without one, anyway. The US Gov does now issue passport cards which are a form of nation

You can't go to Mexico without a passport either. You can't come back without one, anyway. The US Gov does now issue passport cards which are a form of national ID card that allows citizens back in at international LAND borders. You should ask for one when you apply for your passport; they're nice to carry in your pocket when you're abroad and the full passport is safely locked away.