As per IRCC, as a US citizen, you only need your valid passport + study permit + Electronic Travel Authorization (eTA). You don’t need an eTA if you’re arriving by land or sea (for example, by car, bus, train or boat). If you received your initial study permit
before August 1, 2015, you need to
apply for an eTA if you haven’t already done so. If you received your initial study permit
on or after August 1, 2015, you already have an eTA automatically issued to you when you were approved. It’s valid for 5 years or until your passport expires. See your letter of introduction for details. Good Luck!