Yes, we were able to enter Canada with just eCOPR and passport as long as you have US Visitor visa, you can travel by land. You can get taxi service from Buffalo airport (you can check online, taxi from buffalo to niagara falls canada) and they will drop you to Niagara falls, Canada. It costs around 90 USD. The documents that were asked at the border at that time were eCopr, passport, covid negative test report and Vaccination certificate, I guess now covid test may not be needed, you can check that.