They are ironically the opposite of nationalists. Secessionists, Separatists, or at best, Nationalists only for the old Republic of Texas (which was a country after separating from Mexico but before joining the US).
Yes, that's exactly what these asshats are. Texas, not USA, is the "country" they're nationalist about. That's why they call themselves Texas Nationalists not nationalist Texans.
A bunch of them are actually nationalist Texans too but they're too dumb to see the contradiction. Just like they're too dumb to see the contradiction when flying a US flag & a confederate flag together. They're not the sharpest tools in the shed; they'd literally shoot off their own feet if they thought it might pwn the libs.
Ah ok. Yes, these people are being unpatriotic to the US by wanting to secede from the US. But many Texans are more patriotic towards Texas than the US. But it's just because there's a Democrat president. When their believed cheetoh jeezus was in office, no one in TX was trying to secede & it was all "USA USA!!!" I lived in Texas for 40 years & they bring up seceding every few years when they don't like the president. It's really stupid & will never actually happen.