Because America wouldn't let them Be successful.
So your whole argument is that they couldn't succeed on their own because America would undermine them, not because they are incapable due to resources, culture, etc? That did not seem to be the issue being discussed.
What action the United States would take was not really the question. Obviously you could argue that the United States would simply not allow succession at all and declare martial law. The question was, could LA or Texas be successful given a peaceful secession, thus, do they possess the resources, culture, and organizational capability. Is it tangibly feasible?
They would also not have any military of their own and would proabably be invaded for their oil.
lol. By whom? Now you are just throwing out random scenarios of foreign intervention.