U.S. GDP in 2008 was $14.3 trillion. http://flagcounter.com/factbook/us
The public debt estimate for this year is $12.9 trillion. http://en.wikipedia.org/wiki/United_States_public_debt
The total debt (public/private) in the U.S. is $57 trillion.http://mwhodges.home.att.net/nat-debt/debt-nat.htm
U.S. households and non-profit organizations also have a total wealth (assets minus liabilities) of $60 trillion.http://en.wikipedia.org/wiki/File:US_household_and_nonproft_net_worth_1945-2007.gif
What does this mean? Debt, when well-managed, doesn't have to be a bad thing. If someone earned $50,000 per year and had a $50,000 mortgage, that person would be doing pretty well. The U.S. is kind of like that right now. And that is even moreso when one considers the $60 trillion that the country has free and clear of debt.
In 1950, we had a public debt that was basically equal to GDP. During the 1970s, it was actually only 30% of GDP. During the 80s and 90s, it pushed up to 60% of GDP. Today, it is in the 90% range.
The biggest concern is not the debt itself, but the increase in the debt. This was caused by fighting two wars, Bush tax cuts, Bush and Obama stimulus programs, the federal bailouts, etc. Spending is a bipartisan pursuit. And when one looks at the 900 billion cost of health care, it really isn't that big of a number by comparison.
I do think that we have space for more deficit spending in the short term. The jobless rates are just too high. The government needs to keep printing the cash. But it can't go on forever.