Eh... probably wouldn't go as far as saying a passport is not needed. It really helped me when I had to renew my drivers license with the upgraded verification that they are doing. Couldn't renew online and had to go into the DPS office. Took 2 or 3 months and a couple of visits to get it straitened out. Finally found my old (fortunately not expired) passport and was able to use that for my verification. PITA.
https://www.dps.texas.gov/section/drive ... quirements
Valid, unexpired U.S. passport book or U.S. passport card
Back to original subject. I haven't been to Mexico in years but have family along the border that like to cross to get some things. I refused to take my vehicle and the one time I did go where I was staying a couple of days just across the border, I checked my bag multiple times for contraband i.e. pocket knives, firearms, and bullet casings. At one of my former jobs, my boss had a relative fishing on Falcon Lake and strayed over to the Mexican side. They found loose ammo on his boat and he got arrested.