Because TX doesn't have a state income tax, it's not included in the drop-down menu. You should be able to continue if you leave both Boxes 16 and 17 blank.
Please post back if you continue to have difficulty.
*** I am NOT a tax expert. I am a seasoned TurboTax user, and volunteer to provide assistance to TT users. Nothing I post is to be considered TAX ADVICE; I bear no legal liability for responses.***
