从驻多伦多美大使馆得到的权威答案-

再次谢谢8大哥的回复，但是，你看到的信息是不正确的。我也看到一些律师说不可同时持美加国籍。这的确是一个法律是不太明确的issue.

引号源来自大使馆的回信：

"Dual nationality is allowed by the US government.

She will not lose her US citizenship by acquiring Canadian citizenship.

She must always enter the US as a US citizen"

同时，请大家看美驻多使馆的官方website: http://toronto.usconsulate.gov/service/passports-and-citizenship.html),  “A U.S. citizen who naturalizes as a Canadian citizen may generally retain U.S. citizenship.”  “ Determination of dual nationality can only be made by applying for a U.S. passport or registration, not by phone or mail.”