a)So taking on debt pretending to do something good is fine?
What if I say they do something bad with that debt too, is it still OK?
b) Interest rates are being paid for decades via taxes, money that could have been put to use much better. I'd say it's similar enough and don't think "it works differently" is an argument here
It works differently because the US can just issue more currency to pay off debt. Honestly sovereign debt is a currency manipulation / money supply tool more than anything.
What if I say they do something bad with that debt too, is it still OK?
b) Interest rates are being paid for decades via taxes, money that could have been put to use much better. I'd say it's similar enough and don't think "it works differently" is an argument here