IMO, the reasons there was never a significant LCN presence in Texas are:

(1) TX was largely settled by non-Italians, mostly Germans and northern Europeans. Not one of the major TX cities (Houston, Dallas, San Antonio, Austin, El Paso, etc) has a "Little Italy" or Italian section of town. For the most part, the Italian food in TX sucks as result.
(2) TX is a "right to work" state, ie, little to no unions.
(3) The population of TX was largely agricultural until the 50's and 60's. It is hard to extort a bunch of farmers and cattle ranchers, let alone run a book or shy operation.
(4) The TX population was largely conservative Christians (Catholics, Baptist, Methodist, etc) who put on a public face of clean living, but tolerated the vices as long as they were out of the public eye and controlled. You could cross the border into Mexico for most of that, or a hidden away whore house or juke joint. Texans would never go for a NO style French Quarter out in the open.
(5) Lastly, if an Italian went to extort a Latino / Hispanic in Dallas, Houston or San Antonio, anytime in the last 50 years, the Italian would have been laughed out of the place or cut up.

The Dallas family, if you can call them that, was never more than a crew compared to any of the other cities.

The Maceo's probably has the closest thing to a family in Galveston. I have heard they ran a great operation and corrupted the police and politicians from top to bottom.

OC in Texas is all DTO's now. The OMC have a presence, as do the prison gangs, but they are small players compared to the DTO's.