I was on TN visa years ago and was able to enter the US with my driver's license alone. I used to travel between Boston and Ottawa regularly. One of those times was during a move from one home to another and my passport was buried in a moving box. I realized it two hours after I left Boston and it would take me 4 extra hours if I go back. I decided not to. Crossing the border to Canada was smooth. When I came back to Boston, I was stopped at the border. I had my driver's license but no passport/visa. While showing all the cards to prove my identity, a Cigna insurance card dropped out. The stiff officer suddenly became friendly said his daughter was working for Cigna. After a short conversation he let me pass. Canada treated me best and Canadians were so friendly.