So your saying you don't need a passport? I thought that became the rule 2-3 years ago.
For the record I will explain.
You started needing a passport to enter the USA, but not Canada. But because you can't come back to the USA only with a passport, the general rule is that don't travel without a passport because you won't be able to come back to the USA.
Now, because OP has a GE card, so coming back is no issue as GE cards are an acceptable method of entering a USA land border, OP has no problems traveling to/from Canada. Just have your birth certificate ready for citizenship proof.
(source that entering to Canada does not require a passport)
http://cbsa.gc.ca/security-securite/admiss-eng.html