The debt/GDP ratio is a false measurement. You are comparing the debt of *ONLY* the government to the output of the *ENTIRE* economy. That's like comparing the debt on one credit card to your entire income, ignoring your mortgage, student loans, and every other credit card you have.
A more accurate measurement would be to take the aggregate debt that a country *AND* it's citizens owe privately and compare that to GDP. The measurement would be quite different for the US, considering that the entire GDP number has been driven by out of control spending from consumers, equity cash-out, and a housing bubble that is not sustainable.
The biggest problem though, is that neither number includes the whole universe of reality. The debt only includes current owed, but fails to include all future liabilities. Companies are required to report contingent liabilities if they are under contract and are expected to be paid back. The government does not.
If the government were reported like the companies it regulates, the people would be demanding the ousting of most politicians.