The Census Bureau has, at last, begun to release urbanized area data. As Nate Berg notes at the Atlantic Cities, the headline that 80.7% of Americans now live in "urban areas" is a bit misleading. Or at least confusing. "Urban areas" consist of "urbanized areas" and "urban clusters." An "urbanized area" is a contiguous area of at least 50,000 people meeting certain minimum density threshholds. An "urban cluster" is, basically, just a small town -- too small to qualify as an urbanized area, but too densely settled to label "rural." That 80.7% includes a lot of people who live in small towns, far from any place one would call "urban."
If we want to count city dwellers, we should stick to urbanized areas. "Urbanized area" is the best fit for our intuitive notion of a "city." Urbanized areas have at least 50,000 people, which is a reasonable threshhold for separating "city" from "town." The urbanized area boundaries are determined by complicated algorithms that measure density and distance from other dense clusters of people; they are a serious attempt to define who lives inside and who lives outside the city. Metropolitan area definitions are not useful at all for counting city dwellers, since they are typically defined by county boundaries and are not a meaningful attempt to determine where the city actually begins and ends.
What percentage of Texans are city dwellers? 75.35%. Although they comprise three-fourths of the population, the city dwellers occupy just 2.76% of the land. Over half of all Texans live in the urbanized areas of Houston, Dallas, Austin and San Antonio. (9.35% of Texans live in small towns and 15.3% in rural environments.)
Urbanized areas are in purple. The urban clusters are represented by the green dots.
Texas is the 15th most citified state by this metric, more urban than all the midwestern states except Illinois, and all southern states except Florida. And it is more urban than the nation as a whole; nationwide, 71.4% of Americans live in one of the 486 urbanized areas.
Despite the fact that Texas is mostly a state of city dwellers, I'm sure we'll be bombarded soon enough by campaign ads from politicians posing by cow pastures and split rail fences. Because, you know, the real Texas is rural.