In evaluating a company or individual, we look at assets less liabilities to find how much the company or individual is worth. If we did that with America, we'd find out that America is worth a heck of a lot more than the national debt.
Any discussion of assets is meaningless if the asset is neither for sale nor has a buyer. And we're not talking about companies or individuals. We're talking about the land mass of United States.
If you seriously think a "Louisiana Sale" can be done to raise capital to payoff liabilities, then you had better have the legal means to separate them from the union, and find a buyer who can pay what it is worth.
Then you can talk about the land 'real estate' of the US as being an asset to offset its financial liabilities.
OTOH, if the land will not or can not be separated and sold, then it is an illiquid asset and can not be used to offset liabilities.
You wrote: "OTOH, if the land will not or can not be separated and sold, then it is an illiquid asset and can not be used to offset liabilities." Part of the value of your home or a commercial building is the land it sits on, which can not be separated and sold, yet it is still valued when calculating net worth. Do you figure your net worth by including debt on your home but excluding the value of the home?