The IMF finds that, under our baseline scenario, a full elimination of the US fiscal and generational imbalances would require all taxes to go up and all transfers to be cut immediately and permanently by 35 percent. A delay in the adjustment makes it more costly.
"An Analysis of U.S. Fiscal and Generational Imbalances: Who Will Pay and How?" (39 page IMF report)
How screwed are Americas finances ? - this is the IMF version.