Texas shouldn't be a problem, both stadiums have roofs. If FIFA is sensible they'll mandate all the games to be played under the roof. Monterrey will be 35c+ so will probably be problematic, would be best if they're all evening games. Guadalajara humidity will be the problem if it isn't chucking it down, and Mexico City will be ok because temperature is mediated by altitude. I'd worry about the East Coast too, because some of the temperature and humidity extremes seen there in recent summers have been bad, though we saw that huge 40c+ spike in the PNW so nowhere is really immune to high temperatures in the US summer.