National wealthThere are 3 figures attached with these notes.
Fig 1. The x axis is the sum of T securities, savings bonds, other treasury and agency backed Govt supported enterprises (which are components of govt debt) in a year in current dollars. The y axis is the national wealth in the same units. Addition of yearly numbers for components of govt debt to get a cumulative number is not correct because of inflation. This requires an inflation correction using data from Table 1.1.9. Implicit Price Deflators for Gross Domestic Product, [Index numbers, 2005=100], Bureau of Economic Analysis.
Fig. 2. This plot shows the national debt on the x axis and national wealth on the y axis in current billion dollars. This shows that the gross national wealth is slightly more than the national debt. The slope is 3/2.The dollars are current dollars and have not been adjusted for inflation.
Fig. 3. Slope is near 1. Net worth is approximately equal to national debt. The data is from

Cumulative Govt deficit becomes Gross national wealth. Modern Monetary Theory (MMT)  is correct! “Unsustainable debt” is just nonsense.