The USA has bases all over the world, there’s even one in Cuba (which I’ve never understood)

Exactly

If anything that's an immediate foothold and for Texas, a serious defensive liability, not an asset in any way.

Not that anything will ever come of this, but if Texas were to violently secede, it's highly likely that the US could put down the secession, occupy and assume control of the territory, and manage the forced reunification of same...

...all using only the US military forces already within the borders of Texas.

Again, not that it's actually going to happen, but in a just world, we'd let them do it, then occupy the "rogue state" and re-annex them, but as a territory.

Basically nothing changes for the citizenry except they lose the impact of the vote. Texas now gets one non-voting member in each chamber of the legislature, and send no electors to Washington for presidential elections.

They should also lose the ability to govern themselves at the state level and instead, affairs within the territory are managed by a joint panel of provisional military government working together with state department officials and UN observers.

While they're at it, let the US seize and nationalize all corporations, which now roll all profit back into reimbursing the American taxpayers for their trouble and expense of dealing with this Texan nonsense.