上面两位外行了。
美国人对加拿大人的政策是这样的:
Entry of Citizens of Canada
Citizens of Canada are exempt from the visa and passport requirement of Immigration and Nationality Act section 212(a)(7). To enter the United States, a Canadian citizen must be able to establish both identity and citizenship. Documents that may establish citizenship are: birth certificate, citizenship certificate, and passport. Although the Immigration Inspector may accept an oral declaration of citizenship, it is recommended that a Canadian citizen carry a document that establishes citizenship. Under current procedures, all travelers may be required to present photo-identification. NOTE: A Canadian citizen arriving from outside the Western Hemisphere is required to present a passport. Canadian citizens classified as Treaty Trader, Treaty Investor, or Fiancé(e) require a visa.