> The same could be said for Germany and Austria.
Well, yes. The differentiation is both dumb and well-reasoned, depending on your ethics.
However at least germany and austria have meaningfully distinct languages or dialects and many centuries more to marinade in their differences. Texan and californian aren't distinct enough to produce nationalities that are clearly distinct (aside from arbitrary pride!) and they regularly swap populations sufficient enough to provide cultural osmosis that keeps the two cultures tied together.