Determining the exact amount of exposure is nearly impossible until governments start stepping up to the window created by the European Union and the International Monetary Fund to stem the crisis in Greece and elsewhere on the continent.

But one rule-of-thumb formula puts potential US exposure at $54 billion should the entire IMF loan fund be tapped.

And that doesn't count the added exposure created by the Federal Reserve's decision over the weekend to participate in currency swaps to provide liquidity to jittery European banks. The swaps move resembles the Term Auction Facility the Fed instituted when the worst of the US financial crisis hit in 2007-08.

And the entire bailout package has been nicknamed "Le Tarp" by some for its similarity to the Troubled Asset Relief Program that bailed out US companies with taxpayer-backed loans.

US involvement in the European crisis already has drawn critics from Congress and economists who think the domestic financial issues should be cleared up first.

"Inflation and debt is not the answer to a problem caused by inflation and debt," said Michael Pento, chief economist at Delta Global Advisors and a critic of both the European plan and the Fed's approach to US fiscal stability. "It's a European problem that should have been dealt with by Europeans."

In Washington, Senior administration officials said taxpayers will not be liable for the European bailout. (See video)