The deficit mainly matters because we have to pay interest on the loans we take out. If the rates are good, it's actually a great investment. If the rates are bad, it hamstrings future growth, because now the budget is spent paying back old loans instead of building new things.

Well, why can't we just print money? We can, but it runs the risk of inflation. Inflation is historically low, so yes -- we could totally just print a bunch of money to pay back our debts with relatively little risk of inflation in the short term.

Essentially, debt doesn't matter, except that we have to pay interest. Interest doesn't matter because we print money, except that it might cause inflation. Taxes "destroy" money to dampen inflation. Thus, we can pay off our loans, but that might cause inflation, which might require us to raise taxes not to repay the loans, but to prevent inflation.