I have this feeling that what can't go on won't go on. But when will the US hit the wall? How can we have $25,000,000,000,000.00 plus debt and 100,000,000,000,000.00 plus unfunded liabilities and still go on? Will we hit a quadrillion? A quintillion? A decillion? A centillion? Will the Fall be in 2021 or 2525?
A consideration of Modern Monetary Theory may illuminate such questions.
1.) One person's debt is always another person's asset. That 25 trillion debt by the government matches 25 trillion in assets (i.e. wealth) held by individuals. We consider the government debt to be "bad" but the wealth held by people to be "good." So is the situation a net bad thing or a net good thing? It depends on the details.
2.) As a corollary to #1, when the government (public sector) runs a deficit, the private sector runs a surplus. That's math. One is good, the other bad, but they're inextricably tied to each other.
3.) The "unfunded liability" assertions about Social Security is mathematical sophistry and scaremongering. It's not at all unfunded, as long as you consider it a safe assumption that we will continue to have a functioning economy where social security taxes will continue to be collected. The projected costs are just as much assumptions as the projected revenue. It's entirely possible, we've learned, for a substantial fraction of retirees to meet an early demise.
The sophistry goes beyond this. A century ago, a working person might support a household with numerous non-working people. I.e., a spouse, several children, a grandparent or two. The ratio of working people to people being supported was far smaller in the past. It's only the
current structure of the Social Security system that needs to be tweaked. The "crisis" of the "trust fund" can be resolved in an instant, by considering payments to be obligations of the general Treasury fund, and revenue to be deposits to the general fund. Others would prefer a different tweak. It is overall, a non-issue.
Overall, consider that Japan's debt to GDP ratio is far higher than the US. Yet, it's still regarded as a solid economy, with it's currency also considered by investors to be a high-quality asset.