The US military spent nearly ten years trying to take control of Iraq. At no time were there ever more than about fifteen thousand 'insurgents' fighting them. In the end, they never truly conquered that insurgency, but left upon the command of the president.
Now multiply that fifteen thousand by about a thousand and tell me what sort of odds you think the US military would have in taking control of this place. There are more guns per capita here, than nearly anyplace else in the country, and Texans have a strong willingness to defend themselves against any aggressor.
And just how long do you think the rest of America would stand by while American troops fired on their fellow citizens over a political question? Not long, I guarantee you.
If Texas decides to leave the union, she will go, and no one will stop her.
You make valid points. And there will be many freedom loving Americans who will go to Texas to join the fight. The federal government will be at war with patriots from all over the entire country and not just Texas!