Remember a panic out of the dollar is unlike any other currency panic we have seen. As the defacto international reserve currency (though obviously slipping from that status), every country, every international corporation is holding them--all possible points of panic.
A full fledged world panic out of the dollar will mean huge U.S. inflation, soaring gold and the financial system rocked to the core.
How will the U. S. be able to finance its debt under these conditions. This could be the big one.