Your point about the US is valid. However as their national debt is $15 trillion they aren't exactly a model economy.Why are people so obsessed about the debt of sovereign governments these days?
Think about it like this: there is (virtual) money in MMO games. Gold in World of Warcraft, ISK in Eve Online, or whatever. In an in-world accounting sense, this money is a debt (liability) of whoever runs the system. But it is ridiculous on the fact of it to worry about the total amount of money in those systems.
So why is their this obsession with the debt?
The most immediate reason is this gut reflex of "it needs to be paid back". But what one has to realize is that, for a monetary sovereign, paying back the debt is just exchanging one type of liability against another. The debt is money that has already been spent. Paying it back does not create new financial assets, it is just an asset swap. Why on earth would that be problematic?
The other objection is that the interest paid on debt causes an undue redistribution of wealth. That point is one of ignorance: a monetary sovereign effectively sets the interest rate that it pays on its outstanding debt - that is what the monetary policy of the central bank is about.
Seeing the true nature of money is initially scary, and perhaps this is what stops many from a deeper understanding. I can only hope that future generation will make fun of us for the way we are thinking about money.