As you can imagine, it is extremely complicated to put together a balance sheet and calculate a net worth for an entity as large and as complex as the U.S. government. The Treasury Department is responsible for compiling such a balance sheet. The 1995 report attempts to calculate the total assets of the federal government. The government's main assets consist of property and equipment, cash, investments and inventories. These liabilities include debt held as U.S. securities, federal employee pensions and actuarial liabilities, as well as other moneys owed.
Net worth is defined as assets minus liabilities.
Theoretically, if the government were to sell all of its assets to pay down its debt, it would not be able to pay its current obligations.