It's not quite that simple. If you're holding dollar denominated assets and you want to 'suddenly' switch to Euros you'd better be happy to sell/exchange those

It's not quite that simple. If you're holding dollar denominated assets and you want to 'suddenly' switch to Euros you'd better be happy to sell/exchange those assets for pennies on the dollar. Flight from an asset causes prices to crater. Sudden flight and causes crises and panic.