I will try and put some math behind it:
Let's take the
rule of 72, which allows us to roughly calculate how long it will take for the country's debt to double from interest alone if the budget were balanced:
Say the U.S. pays 4% interest on its loans and that interest will never increase for any reason. 72/4=18. If the budget were balanced and the U.S. had a stable 4% interest rate on its debt, the debt would double in 18 years. However, we know that the interest on U.S. debt is not stable, in fact, it is dependent on market conditions.
The budget isn't balanced either and is nowhere near balanced. S.S., Medicare, and Medicaid costs will also likely increase. If we continue down the current path, Moody's will likely downgrade us and S&P is likely to downgrade us further, which affects countries wanting to lend to us and increases the interest on our debt. Europe is in bad shape, restricting the likelihood of their future lending. By 2020, our debt is projected to be $20 Trillion, and that would mean we spend less than $6 Trillion over the next eight years? That doesn't seem likely. Nothing looks good long-term. Looks like by 2020 or 2025 we're going to have over $20 Trillion in debt and a bad credit rating.