I'm somewhat concerned. But what percentage of the GDP does this represent? The absolute number isn't as important as the proportion of GDP we're talking about. If Greece, say, had a national debt of 19 trillion, it would be totally catastrophic. For the US to have a debt this large is extremely concerning, and not good, but given the size of the US economy, this number isn't as scary as it looks.
AFAIK, we've had national debts that were bigger in proportion to the size of the economy in the past -- notably right after World War II, when I think the percentage reached 128 percent, or something like that.
The interest rates on the debt also matter a great deal. Today US interest rates are really, really low, which means we're not paying nearly as much to service the debt as we would if interest rates were higher.
It also matters where we are in the business cycle, when it comes to high government debt. Most liberal economists say that a high national debt can be good during times of recession or depression, when the government needs to spend more money to provide unemployment compensation and SNAP payments to help poor people survive, while also keeping up effective consumer demand. In a recession or depression, a high government deficit and/or government debt can be "counter-cyclical."
As the economy improves, however, many liberal economists would say it's important to reduce the debt levels, so the government will have the flexibility needed to address the next big economic crisis.
Some of the Marxist economists I'm reading are extremely worried about another global economic crisis erupting soon, and are afraid that the high debts the US government is running now will mean it has no effective tools to address the next crisis.
I also think it matters what tools we use to reduce the debt. To cut important social programs for the poor and the middle class in order to reduce government spending is both morally wrong and economically counter-productive, I think. If we "save" money for the government in ways that drive more Americans into poverty and starve the economy of effective consumer spending, it may backfire, and leave our economy worse off than it is already.
OTOH, it makes all the sense in the world to raise marginal tax rates on the super-rich and the corporations in order to bring down deficits and debts, IMO. Of course, the government has to be able to get the rich people and the corporations to pay those taxes, or raising taxes won't work, either.
-- democratic socialist for Sanders / only the truth is revolutionary -- no matter what partisan flavor or "ism" the truth represents.