There isn't a reason to think that the US taxpayer is going to pay back their debts (in real terms). The numbers have gotten large enough relative to GDP that they aren't realistically going to honour those promises.
It may get ugly, but that debt isn't going to last generations.
The biggest loser will be the (US) general public, because it holds the majority of the debt. Foreign adversaries (such as China) hold a much lower percentage of the debt (and USD-denominated instruments).
Seems unlikely. Nobody makes reference to poor behaviour by someone's father's father when deciding to lend.
And it is already embarrassingly obvious that the US isn't actually going to pay their debts back. The people taking on the loans at the moment have hopefully accounted for that.
Is all this debt bad? Yes. Will it affect the prospects of future generations? Only if it spirals into a war and something spills over into the physical world destructively.