What would a natural-born US citizen need to cross the US?
If you're intending on entering Canada by land, make sure you have your birth certificate or certificate of citizenship with you (along with your driver's license). If you have an enhanced driver's license, that would be the best form of approved identification besides a passport. Also, if you're studying in Canada, while a visa is not required, have proof that you're attending school. If you are a U.S. citizen, ensure you carry proof of citizenship such as a passport, birth certificate, a certificate of citizenship or naturalization, or a Certificate of Indian Status along with photo identification. If you are a U.S. permanent resident, ensure you carry proof of your status such as a U.S. Permanent Resident Card. Citizens and permanent residents of the United States who are members of the NEXUS or FAST programs may present their membership cards to the CBSA as proof of identity and as documents that denote citizenship, when arriving by land or marine modes only. Canadian Border Services: Travel Documents If still not sure, you can always call the CBSA and confirm with an officer (8a-4p Monday to Friday possibly after a long queue on hold):Border Information Service However, I hope your emergency won't require you coming back home before you can get your passport; a birth certificate or certificate of citizenship isn't WHTI-compliant. Land or Sea Travel: U.S. citizens entering the United States by land or sea are required to present a valid WHTI-compliant document, which include: U.S. Passports U.S. Passport Cards Enhanced Driver's Licenses Trusted Traveler Cards (Global Entry*, NEXUS, SENTRI, or FAST) Military Identification Cards (for members of the U.S. armed forces on official orders) U.S. Merchant Mariner Document (for U.S. citizens on official maritime business) *The Global Entry (GE) card is only an ENTRY document and may not be used to enter Canada, Mexico or Adjacent Island. US Customs and Border Protection: US Citizens - Documents needed for entry into the U.S.. As with all things requiring identification, your best bet is to be prepared with the proper documents prior to heading out. If an emergency does require you to cross without complaint documents, having enough documentation (that's normally accepted within your borders) may suffice (but most likely you will be subjected to additional screening/interviews). I cannot guarantee it though, and I'd recommend you call the consulate's emergency line, or visit the closest embassy. Embassy of the United States: Ottawa, Canada - Embassy of the United States I hope this helps. If I get comments from better authorities on this subject, then the answer will be amended/updated as necessary. Thanks for reading!