Okay, but it's really not. If I owe you a $100,000 unsecured debt, that's easily a source of friction between us, especially if I come to you for another $10,000. If a country owes you $100 billion, and (let's say) it gets hit by a hurricane that knocks out its electrical grid, you might actually give away $10 billion so they can fix it, because it's worth doing so in order to collect on the $100 billion debt.

After the Revolutionary War, generation and maintenance of sovereign debt to foreign nations was an explicit goal of the early U.S. government, because it presented parties who might otherwise be neutral (or who might even lean towards British sympathies) with a strong incentive to continue to recognize the new government, instead, lest their accumulated debt become worthless in the face of an American collapse. This played out to some degree in 1812, when there was every reason for other European powers to get involved in the war (especially Spain, who could have easily negotiated a southern front in return for e.g. Florida's return), but instead all of them sat on their hands and, in many cases, continued to buy American goods (to the extent that they could get past the blockades).