Get outa here! There's really only two ways to offend a Texan: criticize Tex-Mex food or say you don't care whether the Aggies or the Longhorns win the big game. Just .... don't ... go there. (I'll have mercy on you since you're from Poland and may not know about the Aggies vs the Longhorns:
Texas A&M Aggies Football – The Rivalry with Texas.)
Tex-Mex food is something I'd love to try - I mean the original version, 'cos "Mex-Tex-Polish variation" is the food I prepare sometimes. No calories count, cholesterol level... it must be hot and spicy and eaten with tortillas. Chilli con carne, queso... yummy. Jeez, I feel quite hungry!
As for Aggies vs Longhorns... well - football is not very popular here, unless we speak of European version of football, ie soccer. But I can understand the rivalry of two teams, as we have some similar rivalries here, but not so... well... colorful.
So - to sum up - I hope my version of Tex-Mex dishes wouldn't offend a real Texan.