The Canada-US Border is now open to US travelers. No vaccine or ArriveCAN app requirements. Masks are no longer required in most public places in Ontario, however, there are exceptions such as in hospitals and other healthcare and LTC settings.
All U.S. citizens arriving in Canada must have a valid passport or passport equivalent, such as a passport card or NEXUS card.
U.S. Driver’s License
U.S. driver’s license is perfectly transferable to driving in Canada.
U.S. currency is not accepted everywhere in Canada, make sure you will bring some Canadian currency.