Americans want to pay down the national debt, and if given the opportunity to make a small donation that would be used to pay back this debt (and NOTHING else), I believe many Americans would donate a small sum.
When filing taxes, there is a check-box that allows the filer to donate $3 to the Presidential Election Campaign Fund, which was initiated in 1973 in an effort to place candidates on more equal financial footing. In 2000, $214 million was donated in this way and $35.7 million was donated in 2012 (http://www.fec.gov/press/bkgnd/fund.shtml).
Imagine how much could be generated for paying down the nation's debt. Though it certainly won't add up to the trillions we all owe, any little bit will help. Initiating this would have little/no political or economic impact. Please sign!