The problem with TEXIT is the same with BREXIT and pretty much any libertarian policy in that it expects so many things to stay the same.
As soon as this happens, assuming the US take direct military action, all the US bases are gone. Same with all defense contractors. Technology companies are gone too, they do not want to go through the headache of working with the US a foreign company. That's Texas Instruments and HP.
Taxes will skyrocket. They will lose all the US tax subsidies that allow them to have no state income tax and now they need to replace all military personnel and infrastructure.
They will probably not bottom out but they aren't going to be a world power. They will pretty much be Spain in terms of economy.