Why do you think they aren't? Sure, Texas doesn't have anything like the NSA. Still, you can bet that Texan senators and reps discover things that they aren't officially supposed to know, and some of that information reaches their colleagues back home.

I don't think it's legal to use NSA/CIA to spy on political adversaries and sabotage them politically and economically.

How do you know it doesn't? At some point "spying" becomes just "research".

Even grocery stores do "covert espionage" against their competitors, to e.g. match prices.

You are comparing states with groceries...let's compare the Afganistan war with an afterschool fight or terrorists with pranksters and see where it leads us.

Spying activities are hostile actions. They are used to gain unfair economic advantage, overtrow governments, win elections(for their fav candidate) and other nasty stuff.

If the british government needs more data to find terrorists they could use their political power to improve the data sharing at the EU level.