going to Mexico and my wife's passport had expired, so she made an emergency appointment to get a passport and we went. Came back through at the end of our trip and one member of our party only had a driver's license. They let her back in no problem 🤦🏻‍♂️.

I think you can still get back in with just a license and birth certificate, although you'll be hard pressed to find anything official. I won't travel to northern Mexico anymore, so I couldn't tell you for sure.