As already mentioned, the public debt to GDP ratio is 75% (just under $12 trillion), not a particularly interesting figure -- there just isn't any empirical research indicating that this value has special significance (discredited research indicated that 90% had special significance; see "Rogoff and Reinhart").
Since the public debt to GDP ratio has two inputs, the federal government can continually add more debt to the pile while simultaneously decreasing the ratio. While Washington absolutely needs to address certain fundamental problems (e.g., reforming Medicare, reducing world police-style defense spending), there isn't anything fatal about the current situation even if such work is delayed -- CBO projections indicate it will take another 25+ years for the public debt to GDP ratio to reach 100% if no changes at all are made.
lol, just lol @ all the fear mongering around these issues. Somebody is making a lot of money off of it, but I have a feeling it isn't the people soaking it up.