Normally, when they talk about those shortfalls, they're talking a 75 year time frame.
The figures I've seen for the unfunded liabilities of the federal government are at 59T. That's more that the net assest of the US households
That is similar to noticing your mortgage is larger than your net worth while ignoring your income over the next 30 years.
The demographics aren't being taken into account though. Looking at that over a 75 year time frame doesn't seem to present an accurate picture of the situation if 75% of the liability has to be paid out in the first 25 years.