Not so. According to this source, you can gain Canadian citizenship through marriage. But it’s a moot point anyhow, because the Cruz family lived in Canada for only three years before Ted was born, and Canada required a minimum of five year’s residency before becoming a citizen. Ted’s mother would not have qualified, but even if she had, she could have kept her U.S. citizenship.
Both the U.S. and Canada allow their citizens to hold dual citizenship with other countries, and therefore it is legal for you to hold a U.S. and Canadian citizenship while residing in either country. To qualify for Canadian citizenship as a U.S. citizen, you must either be the child of a Canadian citizen, a grandchild of a Canadian citizen, or a spouse of a Canadian citizen. The application process and requirements vary for all cases and connections.
Read more : http://www.ehow.com/how_5569183_dual-citizenship-canada.html