From the link:
Numerous economists have expressed optimism about Iran's ambitions, saying that the impact of the Iran oil bourse on the American dollar-and U.S. economy could be worse than Iran launching a "direct nuclear attack."
While the article is somewhat dated and keeping in mind the need to consider the source, aljazeera.com, it still speaks to the implications of their effort.
And this (also dated) article:
The Bush administration will never allow the Iranian government to open an oil exchange (bourse) that trades petroleum in euros. If that were to happen, hundreds of billions of dollars would come flooding back to the United States crushing the greenback and destroying the economy. This is why Bush and Co. is planning to lead the nation to war against Iran. It is straightforward defense of the current global system and the continuing dominance of the reserve currency, the dollar.
With economies so interdependent and interwoven, a global, not just American Depression would occur with a domino effect throwing the rest of world economies into poverty. Markets for acutely less expensive US exports would never materialize.
The result, some SME's estimate, might be as many as 200 million Americans out of work and starving on the streets with nobody and nothing able to rescue or aid them, contrary to the 1920/30 Great Depression through soup kitchens and charitable support efforts.