查官方規定比在這裏問可靠。

Crossing U.S. Borders

• U.S. Citizens
• Lawful Permanent Residents
• Citizens from Other Countries
• Trusted Traveler Programs

U.S. Citizens

Air Travel

All U.S. citizens including children must present a passport or other approved travel document when entering the United States by air. U.S. citizens can present a passport, NEXUS card at airports with NEXUS kiosks, U.S. military ID with travel orders, or a U.S. Merchant Mariner Document when on official business.

Land/Sea Travel

Beginning June 1, 2009

• U.S. citizens entering the United States at sea or land ports of entry are required to have documents that comply with the Western Hemisphere Travel Initiative (WHTI), most commonly a U.S. passport, a passport card, a trusted traveler card such as NEXUS, SENTRI or FAST, or an enhanced driver's license. See the complete list ofWHTI-compliant documents.

http://www.dhs.gov/crossing-us-borders