No ... you must show proof of US residency, and pay taxes like the rest of us, hence the need for a SSN.
You can not use a Canadian SSN to work in the US
As of 2011, gay people can freely join the US military and do not have to hide their orientation.
Yes
No, you cannot.
Not in the US military, no.
Sir Yes, Sir!!
You don't. You need to be in the US.
U.S army
Yes. You can join the US military without being a citizen, so long as you've established permanent residence and have declared an intent to obtain citizenship.
Yes, you do need a SSN to get a checking account in the United States. You must provide an ID and also your SSN.
One can join the US military as young as seventeen (17) with parental consent
The Coast Guard is a branch of the US Military, so yes.