I have less information about abroad but i must say something that we have to reason collectively,
Out of 195 countries in the world i know too well that most of the population (country's) are solely depending on USD, EURO, POUNDS, YUAN for major trade. I mean before anyone could trade among these 195 you need any of those currency to be able to travel across, and if only 6 countries decides to breakout from USD how do you think it will affect the US dollar?