At least 3 of the 5 generally accepted style guides say "Texas's" is correct. It's acceptable under the other two, but not preferred. But, whatever. You do you, chief.
https://www.google.com/amp/s/www.proofreadnow.com/blog/bid/84201/Possessives-Proper-Nouns?hs_amp=true
It's also "acceptable" for your man-thong to be showing outside of your low rise skinny jeans, but that doesn't make it any less embarrassing.