yes
The American government
yes
No. He also needs a visa issued by the Canadian government.
Oh, like... 5 to 8 years!
No. Assuming that there are no other legal impediments to your entering Canada, you could get into Canada. You could apply for permanent resident status - something you should do BEFORE you arrive in Canada. Being married to a Canadian citizen would probably be a big advantage. Getting Canadian citizenship is a whole other process. Before you can apply, you have to have lived in Canada for three years without interruption or, in some cases, for three of the last four years. If you meet all of the requirements, THEN you can become a Canadian citizen. Being married to a Canadian will help with that. But marrying a Canadian will NOT automatically make you a Canadian citizen.
They are American.
Unfortunately, no -- at least in the United States. The Federal government does not recognize marriages between people of the same sex. This law is called "The Defense of Marriage Act."
No Green Day are American
When a marriage has been annulled it is considered as never having happened, at least from a sacramental point of view. Where the original spouse or the prospective spouse comes from is irrelevant. Those who have had a marriage annulled by the church are free to marry, period.
No. You do not become a US citizen by marrying one. That is for you to earn by your own abilities!
Green Day
Danny Green is an American basketball player.