International Students who are traveling outside of Canada and are only traveling to the United States may not be required to have a valid Temporary Resident Visa (TRV) to return to Canada, as long as their Study or Work Permit is still valid.1
You may require a US Visitor Visa to travel to the United States.
For more details, please see the Immigration and Refugee Protection Regulations, Section 190 (3)(f):
“A foreign national is exempt from the requirement to obtain a temporary resident visa if they are seeking to enter and remain in Canada solely
(f) to re-enter Canada following a visit solely to the United States or St. Pierre and Miquelon, if they […]
(i) held a study permit or a work permit that was issued before they left Canada on such a visit or were authorized to enter and remain in Canada as a temporary resident, and
(ii) return to Canada by the end of the period initially authorized for their stay or any extension to it […]”2
You will need a valid Temporary Resident Visa, if you are traveling to any other countries, and you are from a country which requires a visa.