Interest has not become a huge issue, but in any case - so what? They got the money for cheap, it has (presumably) fueled growth. Beating 1.5% over five years is not difficult - the idea is to borrow money to accelerate growth - increase prosperity of America, which would return more than 1.5%. Not all debt is bad.
This requires allowing the government to consider tax income as a revenue stream, which isn't playing well politically right now. We're supposed to think of taxes as money the government had no right to collect in the first place, and which the only right thing for it to do with is give it back.
Having a free floating fx sovereign currency issuing regime such as the US,UK,Japan. The federal debt is equal to the private sector savings. Paying of the debt eliminates our savings. This would throw us into great depression ii. We should have perpetual deficits.