What do you think these guys are going to do, line up and wait to be carpet bombed? Guys who are essentially illiterate farmers have managed to keep insurgencies going against the US military for around 15 years in Iraq/Afghanistan. There's not an unreasonable chance that the dumb rednecks of Texas could do as well. But, these guys aren't all dumb rednecks - they're going to have support from a decent amount of people with US military, national guard, police, etc. experience. No one is claiming that they're going to march on DC and take over the country, but they could certainly turn sections of the US into something akin to the Syria/Iraq civil war situation.