“There isn’t any reason the states cannot pick up where the Feds left off.”
They actually have an obligation to protect their citizenry.
The cost will be prohibitive to complete, and no doubt the Left will find a thousand snares to impede and sabotage (like the endangered Artic Rat Lungworm, or some such), but they have a duty to do what they can.
I believe the Texas state budget is up to about 112 billion per year.
Relative to that, I don't think that the cost to complete the wall in Texas would be a lot.
Since non-border states are then freeloading if Texas picks up the cost, I would suggest countersuits against non-border states and the Fed gov to recover it. Plus I'm not sure the cost is "prohibitive," considering the cost of illegal immigration to the state in crime, public health and education.