http://www.masternewmedia.org/news/2006/01/23/the_iranian_oil_exchange_proposal.htmIn the 1972-73 timeframe, the United States government changed its currency from the Gold Standard to the Oil Standard. They did this by brokering a deal with the House of Saud: we shall recognize the legitimacy of your regime in exchange for your accepting only US Dollars as payment for your oil. The rest of OPEC followed suit; in the 1970s, the only people who had oil in the ground were the United States (who obviously accepts the US Dollar as payment for its oil), OPEC (who, following the lead of the House of Saud, only accepts the US Dollar) and a buncha commie bastards we didn't give a shit about anyway.
If you want oil you need dollars; if you have oil you can always get dollars for it; dollars are a good respectable currency honored the world over. You can go to Mr. Lee's Yakimandu Stand in Ulsan, Korea, where there is no US presence, pull out a fistful of dollars and get some Yakimandu. You can go to a snack bar in Miedzyrzecz, Poland, and eat for dollars--and the only American in Miedzyrzecz would be you. You can...you get the idea. The US dollar is the world's reserve currency. Anyone will accept it. But to get it, you have to sell something directly to a dollar-using country, sell to a middleman country or enter the currency market--which, thanks to commissions and fees, is the least-desirable way of doing it.
A Euro-denominated oil bourse (bourses are commodities exchanges; the big ones are the London International Petroleum Exchange and the New York Mercantile Exchange) would destroy this dynamic. A country whose native currency was Euro would be able to buy oil without incurring exchange fees. A country whose native currency was neither dollars nor Euro would be able to trade in the currency whose exchange rate was the most favorable on the day the oil was purchased. Basically, two currencies on the oil standard would damage them both.
Bush isn't worried about the Euro bourse's effect on the Euro, though; he's worried about its effect on America. He's right to worry; the four wealth-creating industries (mining, forestry, agriculture and manufacturing) are all hurting because of things like the Least Expensive Country economic system. Unfortunately, how he's going to keep the dollar from crashing is not the long, painful process of re-establishing a manufacturing base in the US; he's going to go to war against Iran.