First off the place will need to convert from USD to their own concept of money.
There are many economies in the world that use US dollars. When I have travelled abroad I have had no trouble spending US dollars. I have not been to Europe and I have heard it is a problem in Europe. Several countries at one time or another have adopted US dollars as the de facto currency for periods of time when their own currency was unstable(Cuba in the mid to late 90's being a good example). Other countries have backed their currency with US dollars(Argentina did this in the late 90's I believe, and there are several still doing it).
If they wanted to make their own currency it would be very difficult, but the country could easily adopt a foreign currency without trouble and it eliminates a good part of the countries overhead related to currency controls/market. There is of course the downfall of not being able to implement those controls.
To avoid spending all the money you have to export as much as you import. No single state has the products to accomplish this.
The US in its entirety does not come close to doing that either. This would be a problem, but it would be a problem that would follow them from the US, not be created when they leave.
The real problems would be border patrol and national defense. Right now Kentucky and even Ohio's federal tax dollars subsidize programs like the border patrol which they basically don't use(Kentucky has no international border, but maybe Ohio has a few BP agents on lake Erie). I doubt Texas would want to fight the Mexican drug cartels on its own, even if the US did not directly attempt to pull it back into the union by force. Montana would be in a better position, but even they would have some trouble. On the other hand Texas would probably go for a little more extreme border protection policies than the nation in general(along with the other SW border states).
If the US sealed the border and cut off all trade that would obviously create huge short term problems. Probably long term, but at least short term. Of course, there would be pipelines the US would have trouble doing without. I believe a large amount of Texas's water supply flows from rivers which are outside its territory. Of course many would likely leave the state diminishing its water problems. Many many more problems. Again, Montana does not share many of these likely problems. It also doesn't have much of anything in general(Beautiful country aside).
Where is my explanation of how it is legal with citations? I would really like to know where people are getting that secession is legal. Not saying all other things considered in favor of secession a state should not secede simply b/c it is illegal. Rather it is one of those situations where you knowingly break the law and hope you get a way with it, in this case win, so you do not suffer the consequences.
Originally Posted by BryanP
They also suck as a citizen and I have no interest in listening to them gripe.
Well at least we all see to have found one thing to agree on