Shouldn't Europe be forced to repay the Marshall Plan?

For all those griping about the "debt" the US owes, why don't we call in our loans for the Marshall Plan. Only Belguim ever repaid their share of the billions (in 1940 dollars) we spent to rebuild Europe after World War II. Why do WE have to pay our debts but France, Germany, Italy, and even Great Britian don't? What's a few billion dollars over 62 years at 8% intrest?