A. We (if you are refering to Texas)don’t need or WANT illegals more than any other part of the country.
B. You need to study YOUR history.
Sovereignty was NOT lost due to the War Between The States, only the right of secession, and that is even questionable.
So try to secede again and see where it gets you.
The Constitution applies nationwide and that includes Texas. As I said before, if any state tries to ban personal ownership of firearms there will be a bunch of converts to the application of the Second Amendment to declare unconstitutional a state law.