I am a Canadian citizen and have recently started university-level studies in the United States. If I am asked about my country of residence, what should I say?

It would depend on whether you're still considered a Canadian resident or not. 

 

If you are unsure of your residency status, you will need to contact the Canada Revenue Agency (CRA) and confirm it with 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