Governments tend not to "repay" debt, nor is it efficient to do so. The question shouldn't be, "When will United States pay back all this debt?" The question should be, "When will the US economy grow faster than its debt obligations again?"
US debt stood at 63% of GDP in 2007, right before the 2008 recession. Today, that debt stands at 131.5%. This is concerning.
However, just because we are currently doing pretty bad on deficits, on debt, and so on, doesn't mean these trends will remain steady. United States can certainly solve with these issues, but only if there is political will to do so. There is certainly capacity and capability to do so. If you are an American, this state of affairs should worry you. Especially if you believe that there is a conflict brewing, a conflict that we must win at all costs. The current trends are not encouraging.