The tax liability levied upon U.S. citizens is one of the crucial elements that give value to the U.S. Dollar as a world reserve currency.
Since I have mentioned on this blog that sovereign governments will likely "mean revert" to different forms of organization (likely rejecting republican democracy in favor of simpler, more historical arrangements), what other currencies might fulfill a desire to place capital?
Since the Euro area will likely be relegated to the scrap heap of history, The Vatican can revert to issuing its own currency which may carry reserve currency status.
What about a currency based on Islam? On Buddhism?
My point here is that currencies can form balkanizing points just as well as geographical boundaries on a map.