Just in land assets - The Federal government owns 640 million acres of land. Including 47% of all the land in the west. 60% of Alaska is owned.
For example, if an individual owes 120% of their year income. Is it that bad, when that individual owns assets valued at 5-10x that?
Would the US sell off these assets? Probably not. But, it is an option. And they could sell some of these to US citizens or to the states.
But, the Federal government is incredibly asset wealthy in comparison to a simple debt vs GDP ratio.