I am an international, graduate student from the U.S.. Do I need to file Canadian taxes if I made less than $4,500 last year as a graduate teaching assistant?

If you are not sure if you need to file a return, you can contact the Canada Revenue Agency (CRA) and ask them. 

If you are in Canada or the United States, you can call the CRA at 1-800-959-8281. If you are elsewhere, you can call 613-940-8495. This page has more ways to contact the CRA: Contact the Canada Revenue Agency