No major company would willingly operate there after Texas gets hits with sanctions
Who is going to hit Texas with sanctions? The UN? China and Russia would veto and Security Council resolution out of spite. South and Central American nations wont do a thing because Texas is a primary link to the United States so they'll need good relations with Texas just to trade with us. NATO will treat it as an internal matter especially since most European economies are in such poor shape.
As for a military response, I'll wager that is an order that is never carried out.
"You can build a throne with bayonets, but it's difficult to sit on it." - B. Yeltsin