Can a US Citizen become a dual US/Canadian citizen?

Yes you can and marriage has nothing to do with it - well not much.

A US citizen can become a permanent resident of Canada by applying and being accepted. After living in Canada for a period (like 3 out of 5 years or something) they can apply for citizenship. Canada doesn't really care about dual citizenship, the US doesn't really like it but unless you thumb your nose at them in a big way they will ignore it.

www.cic.gc.ca is the immigration website and getting married is not really a shortcut, it helps but it won't make you a citizen.

Yes. Both the US and Canada allow dual citizenship. I am a dual citizen US and Ireland. My wife is a dual citizen also. We are both well over the age of majority (AARP members).

No, I have a cousin who married a Canadian and moved there from the United States, The U.S. government allows it but not the Canadian government. Hope that helps

Immigrate to Canada, do the citizenship thing

The US doesn't recognize it, but no difference

No, you cannot because you may only become a US citizen. That's really the way it is. Yeah, it sucks.

America does not permit dual citizenship of people who have reached their majority.

Yesa but can not hold office