The budget estimates mandatory spending will be $2.841 trillion in FY 2020. Social Security was by far the biggest expense at $1.102 trillion.
Medicare was next at $679 billion, followed by Medicaid at $418 billion.
https://www.thebalance.com/u-s-federal-budget-breakdown-3305789
You have a point. Also, there is a VERY good point made by liberal economist Robert Eisner back in the 1980s (I think accidentally, cuz Reagan was president).
Eisner argued, correctly I think, that American government assets are not accurately valued due to arcane laws that require the government to value an asset at PURCHASE price. So, for example, the Presidio in SF that was sold off several years ago. This was prime urban real estate. Now, I’m no realtor so I can’t give you a square foot valuation for SF property, but the government sold it at a tiny fraction of that.
Or, take our US gold holdings which are substantial. Those are valued at the purchase price (in some cases, $35 an ounce!) When Eisner recalculated the value of American assets in modern $, he found our debt (which at the time he did the study was something like $1 trillion or less to actually be more like $200b, or about 20% of the real debt.
Now, of course people say “We can’t sell the Washington Monument.” No, but we COULD sell some of the DC office buildings and, as Trump has already done, start moving people to much cheaper quarters in the heartland where their offices belong.
However, I think anyone at this point expecting us to dump SS or Medicare is dreaming. It just isn’t going to happen. A VERY powerful pres with full commitment of Congress could reform it so people could opt out, but that would take a near miracle.