CORRECTION: Upon some deeper diving, it seems the trust fund is in fact designed to be 'backed' by treasuries (this was my mistake; not nostr:npub1ath4je07y7py74nvu044fum3f8hz3exc3dtcv782qg94w5gaddusl74k6d'); so, if I understand it correctly now, the ~$2.8T is already reflected in the total debt.
This is a really good explainer by nostr:npub1ath4je07y7py74nvu044fum3f8hz3exc3dtcv782qg94w5gaddusl74k6d on the U.S. social security trust fund.
The trust fund only exists as an accounting fiction. That is, there are no assets backing it up. Put another way, it could have been designed to be backed by treasury bonds, for example, but the issuance of those additional treasuries (i.e. government liabilities) would consequently just push the national debt higher by the same amount (currently about $2.8T). Regardless, everyone - even the government - expects it to be in the negative in about 10 years, so there won't even be any fictional assets anyway.
Discussion
Thanks for comments. Brass tacks, for the negative $150 billion a year deficit that Social Security runs each year, that net negative amount is added to the debt.
It doesn’t matter if the Trust Fund existed, or not, what I just said would occur the same each year.
It is true that, technically, the Trust Fund is “off balance sheet” of the Treasury and holds assets, but those assets are just “receivables due” from other branches of government. And the government doesn’t run surpluses, so again, you just get back to creating another $150 billion in debt each year.
And that means, for all those prior surpluses in Social Security since the 1930s, that money is gone, and these new deficits are in fact “taxed twice” in the name of Social Security.