I am not sure about california, but I can confirm that Texas beef is essentially all grass-fed. This is from observation and from speaking with ranchers I know. Grass-fed also has a better taste, in my opinion.

There is nowhere near enough grass to feed nearly all Texas cattle to marketable size in Texas. Nearly all commercial cattle are bred and born in Mexico from US genetic stock and transferred to the US for fattening with cattle feed because it is cheaper to breed in Mexico and feed in the US. Last I checked only about 3% of US beef was fully grass fed. So it's fully possible you know some grass fed ranchers, but it's unlikely that the second biggest export in Texas is possible without massive amounts of cattle feed. Grass fed beef tasting better is subjective but the costs associated with the process appear to dictate that to consumers it's something they are willing to pay for.