The questions of deficits and debts are not at all black and white. For example, they're gray enough to hold the $14 trillion US debt and leave many well intentioned people arguing whether this is good, bad, or indifferent. There is no formula for how much debt is too much, particularly if you're a nation state, and a nation state that prints their own currency. Now individuals, businesses, or other non-money printing entities find out when debt is too great when they can't pay off what they have and no one will lend you anymore money. However, if you can print your own money, in the end, the only real measure of too much debt is inflation and/or the destruction of the currency.
Deficits and debts are effects with underlying causes. All debt isn't bad, in fact investment debt, that is something which over the course of time will be paid off and creates more wealth is both necessary and good. However, debt created to simply continue an untenable status quo is bad debt, leading eventually to insolvency. And this is the great question of American debt, both public and private. Rob Johnson of New Deal 2.0 has an important talk looking at America's debt question. It accompanied a longer paper he co-authored with Tom Ferguson and that is well worth reading.