Not arguing with your formula, but how do you determine the net worth of a country?
You nailed it --this is the key.
Net worth is assets minus liabilities. We got lots of good numbers on public debt which is currently (from here) $8,413,248,232,387.89. It's the assets that get people messed up. We can't count expected revenue because that's income and not assets.
We can start with 900,270,200 acres of government land and if it's worth $9,345 per acre then our net worth is zero. If we add in the physical capital assets like buildings, then we know we can get a higher number. From just '62 to '95 alone we've spent $4,204,249,000 on that stuff. Real estate values have gone up. How about the gold in Fort Knox? Where we stop is when we look at the really good stuff (from this link):
The Government owns significant amounts of land and mineral deposits. There are no official estimates of the market value of these holdings (and of course, in a realistic sense, many of these resources would never be sold.... ...These estimates omit some valuable assets owned by the Federal Government, such as works of art and historical artifacts partly because such unique assets are unlikely ever to be sold and partly because there is no comprehensive inventory or realistic basis for valuing them.
The bottom line on "net worth" (pun intended) is that the US government is not a business, not supposed to be a business, and it's not supposed to have a net-worth and it will not go bankrupt.