There has been talk in Europe about American hegemony being somehow based upon the use of the dollar in the world. I just don't see that connection at all.
Chances are the movements of the euro as against the dollar will be relatively moderate.
The dollar is currently the principal reserve currency in the world.
The major material advantage, financial advantage from having a reserve currency is that between 200 and 300 billion dollar bills, that may be twenty, fifty, hundred dollar bills as well as ones, exist in the world - a lot of them in Russia as you all know I'm sure.
The prices of all imports would rise if the dollar depreciates.
So you can be pretty sure that central banks around the world will not start dumping dollars on the market in order to buy euros.