You're never going to get me to argue that Chicago Mexican isn't great, it is IMO, undebatable, unless you want to drill down to specifics like street cart fish tacos.
But in Houston, you can swing a cat around and hit a half dozen really good SE Asian dives where you can eat well and relatively cheaply. Especially Vietnamese/Cambodian. I'd even venture to say that if one really loves that cuisine, Houston is a destination city (unless you're on the West Coast, where you head to San Jose or Garden Grove). For BBQ, yeah, you're probably best off sticking with known quantities like Gatlins, Pit Room, Pinkerton's or Roegels.
There's a whole lot of "when in Rome" that applies to eating well and cheaply in the US while avoiding chains. If you're trying to find good pizza in TX, FL, AL, TN or even a food city like NO, and expecting that to rival the pizza belt, you've got warped expectations. Read the room.