Yes, a legal marriage in any country is recognized as a legal marriage in the US. You cannot legally get married in the US if you are already married in another country. What you can do is file the marriage document in the County office. Addendum: It should be noted that, under DOMA, only marriages between one person who is legally female and one who is legally male will be recognized. The rest of us are still waiting for reciprocity.
yes
no
no
I do not believe there is any prohibition against it. If Canadian citizens can (and DO) own property in the US I have every reason to believe that US citizens can own land in Canada.
The child is entitled to both nationalities. Contact the nearest US embassy or consulate general and apply for a certificate of registration of birth abroad.
They are not. Most Canadians are very happy they are not US citizens.
Tens of thousands
yes
No. Marrying in a different country doesn't affect citizenship.
If you are both United States citizens it is not illegal, wherever you are married.
no