The IMF and the European Union have pledged $145 billion to help Greece better handle its debt. The U.S. is a chief contributor to the IMF and would be responsible for a large portion of what the IMF pays to Greece.
Since the turmoil in Greece, other EU countries have acknowledged problems with their debt, and the IMF and EU have upped the bailout to roughly $1 trillion.
The GOP bill, titled the European Bailout Protection Act, prohibits any funds that have been drawn by the IMF from financing an EU bailout until all EU nations are in compliance with their debt-to-GDP-ration requirement. It also requires the Treasury Secretary to oppose any IMF loans until all EU countries abide by the aforementioned ratio.
Under these requirements, the U.S. would be prohibited from participating in the bailouts proposed recently by the EU.