The problem with your analysis is that is is rooted in OUTDATED economic theory. Your opening statement implies a Keynesian view point (Liberal/Democratic approach), but much of the rest of your article seems to hew toward classic economics (Say's Law, Republican orthodoxy).
So called "entitlements" are NOT unsustainable. The USA has the money not only for the current programs but to even add single payer health care. The problem is not debt or lack of funds, but rather a terrible allocation of those funds in society with tax policy skewing the benefits to the wealthy and well connected.
"High-income, and especially high-wealth, filers enjoy a number of generous tax benefits that can dramatically lower their tax bills. Eliminating or limiting these preferences would make the tax code more progressive and push back against inequality. It also would raise significant revenue that could be used to fund key priorities and help address the nation’s fiscal challenges" [1]
Certainly, one can find waste in government spending and programs. That is why we need a robust inspector-general programs, the kind of inspectors neutered over the last four years.
Budget deficits may or may not be a problem. But it is a problem if we focus on that as a metric rather than actual real world outcomes. [2]
The national debt is ALSO not the problem that it seems. US investors own 32.5%. The money basically stays here. The Federal Reserve owns 11.2% and the US government itself owns 27% - both of these are effectively LEDGER COLUMN notations.
Foreign interests own 29%, but they do so because the US Dollar and our economy is considered a secure and safe place to do business. [3]
Ms. Reiff claimes "Routine deficits are not bad; perpetual ones are a serious problem." Based on what? Again I would refer you to Kelton's book (notation below). Ms. Reiff is of course drawing on historical patterns largely based on old economies under the gold standard, or even modern economies of poor and third world nations who are subject to the juggernaut economies of the EU, China and the USA.
You are exactly right about MMT- it does explode the old framework, which needs exploding. MMT exactly explains the discrepancies you note, but fail to answer with your standard resort to mainstream Keynesian/Classic approach.
[1] https://www.cbpp.org/research/federal-tax/substantial-income-of-wealthy-households-escapes-annual-taxation-or-enjoys
[2] The Deficit Myth by Stephanie Kelton
[3] https://www.marketwatch.com/story/heres-who-owns-a-record-2121-trillion-of-us-debt-2018-08-21#:~:text=Some%2070%25%20of%20the%20national,information%20from%20the%20U.S.%20Treasury.
