Whilst I admire Texas for sticking to principles...IF she ever excersised her power and left the Union...firstly...I'm not sure there would be the war everyone thinks there would be...after all, she does have a legal get out clause unlike any other State, she is permitted to leave if she wants.
HOWEVER...if she left, and was a success, (this might not be the best financial climate to try going it alone)
then TRUST ME, other States will want Independance aswell.
Texas is in the best possible Geographic Location, except for Hawaii, and the one up near Canada....is it Alaska?? those Three I reckon could break away and be fine...however...without allied forces consistant to the Civil War divides, many States on their own could not break free, because they are landlocked by the United States...and they wouldnt be able to break as cleanly in a legal fashion as Texas.
Coastal and those States with North Boarder to Canada, and a South Boarder to Texas would be those with the most potential...better still if you have coast AND one of these boarders.