Well the point is, if you take any other person, or company, not government, and you say, this is how much debt you have, and this is how much you take in (I don't have the figures in front of me right now), in all logic you are deeply broke and probably can't recover. However because it's the government and you can print endless money and pull large financial tricks you can claim you're not 'bankrupt'. That's the point.
It's not that the government is bankrupt but that if it was any other entity it would be. So how can't that raise red flags when the government just continues with business as normal? Obviously they have no intention of actually getting out of the debt, instead they'll tax and or devalue currency to make up the shortfall. It's non-sustainable.