As of July 1, 2009, no one can cross the border from Canada into the United States with only a birth certificate. To enter the United States, a valid Canadian or U.S. Passport must be available. This stipulation applies to everyone, including infants.
Canadian residents can also enter the United States using a Nexus card. Low-risk, preapproved travelers use this card. However, not all Canadian airports participate in the Nexus card system.
If crossing the U.S./Canadian border by land, a person can use an enhanced driver's license. This is a form of identification designed to make travel between Canada and the United States faster and easier. A U.S. enhanced driver's license is a kind of combination driver's license and passport. It provides proof of U.S. citizenship and can be used by U.S. citizens to enter the country via land or sea from Canada, Mexico and the Caribbean.
A Canadian enhanced driver's license is only issued to Canadian citizens. The applicant must provide a nominal fee and a completed citizenship questionnaire. In addition, the applicant must have no travel restrictions. Both the United States and Canada require the applicant to reside in the province stated on the questionnaire. However, not all provinces issue this license.