But this really isn’t about justifying spending as a moral good. The main changes which accelerate this debt are tax breaks for the wealthiest.
Welfare spending and public investment are about a shared sense of public good. That’s really what the US lacks, compared to European countries which support much higher levels of public spending with (historically at least) very broad public support.
Spending someone else's money is pretty fun, especially once you find a way to justify it as a moral good.