Many Canadians, formerly from the USA, worry about the legality of dual-nationality.
Never fear! It is perfectly legal to be a citizen of both Canada and the USA at the same time.
The US Embassy in Canada confirms this to be true.
The US laws against dual-citizenship were repealed during the Eisenhower and Johnson regimes.
US law does not mention dual nationality or require a person to choose one nationality or another. Also, a person who is automatically granted another nationality does not risk losing U.S. nationality.
Based on the U.S. Department of State regulation on dual citizenship (7 FAM 1162), the Supreme Court of the United States has stated that dual citizenship is a "status long recognized in the law" and that "a person
may have and exercise rights of nationality in two countries and be subject to the responsibilities of both. The mere fact he asserts the rights of one citizenship does not without more mean that he renounces the other", (Kawakita v. U.S., 343 U.S. 717) (1952). In Schneider v. Rusk 377 U.S. 163 (1964), the U.S. Supreme Court ruled that a naturalized U.S. citizen has the right to return to his native country and to resume his former citizenship, and also to remain a U.S. citizen even if he never returns to the United States.
So get BOTH PASSPORTS. It never hurts to have a back-up passport.