Leash laws for cats are up to individual cities or towns, not the state of Texas. Leash laws for cats are very common in Texas and many of the cities (both large and small) have them. Large cities such as San Antonio, Dallas and Houston have leash laws for cats. The website of a city will have leash law information.
I live in Gilmer, TX. and my neighbor has 5 cats that run the neighborgood. I will have traps set to catch them if I catch them again on my yard. I am not a cat hater, but my yard is mine, not the cats.
Texas actually has two laws for your feline-one states that cats may be outside as long as they are on a leash, or in a fenced yard, the other states that the cat must be under the owner's immediate control or on the owner's property.