When secession was brought up a decade or so ago the naysayers pointed out that if Texas wanted to secede it would have to purchase all of the federal projects (highways, dams, military bases, etc.) from the feds. This doesn't seem fair as Texans helped pay for those. However, they paid for them as US citizens and not as Texans.
Also, the Deep State will sow uncertainty about what will happen to government programs like Social Security, Medicare, Medicaid, Welfare, Fannie Mae mortgages, etc.
So-called conservative retirees will be scared into voting to stay.
Math is not your strong suit. Instead of filling the US Treasury with payroll taxes, those taxes would be going to the Texas Treasuery, get it? Secession does not mean taxas are no longer paid. Same amount of money paid, different (better) management of those funds.
Learn: Dissolution of the Soviet Union