[Army Air Corps]

What will happen when Texas opts to leave the U.S.?

Speaking of that.

[William Tell]

From the article you linked: "The various theories of nullification and secession bandied before the Civil War, by John C. Calhoun and others, were clearly unconstitutional."

Here's a quote from the Articles of Confederation which preceded our Constitution:
"[T]he Articles of this Confederation shall be inviolably observed by every State, and the Union shall be perpetual;"

I'm not aware of any similar statements in our present Constitution.

The U.S. Constitution became ratified when 9 of the original 13 colonies approved it. How would it be possible for the first 9 to bind the other 4 to a Constitution they didn't approve?

A majority of Kalifornians are unwilling to bear arms in order to protect their own families. What possibility exists that they would bear arms in order to force Texans to stay in the Union?