On the contrary. As to national debt, it *is* sustainable, after all, we're not in default at this point. If we cut off our deficits, and are able to refinance at current interest rates, the debt will be sustainable for 30 or 40 years. It's possible, with a decrease in spending, to reduce the debt.

The part that isn't sustainable is Social Security and Medicare/Medicaid. The solution to the projected Social Security shortfall is to revise the actuarial assumptions about Social Security to the equivalent of where they were in 1937, where the life expectancy was 59 years, whereas now median life expectancy is almost 20 years greater. This might mean setting the retirement age for people who were born in, say, 1948 and beyond to 75 years of age. It could also spell the end of the Social Security Disability Income program, and benefits to dependents. As for Medicare/Medicaid, the program faces imminent insolvency, so the solution might be a lot more drastic, perhaps involving the drafting of doctors and medical personnel into the Public Health Service (whose chief officer is the Surgeon-General) and the provision of medical care at reduced pay. Actually, what's more realistic is that the medical-industrial complex will collapse, being unable to sacrifice the smallest amount of its prerogatives, perhaps aided by persistent and incurable insolvency on the part of third-party insurors.