I for one don't believe the crashes were engineered (not implying that you do), or that the Fed let them happen - instead I think no one and no agency can control the economy - I think they have some power to make changes that can sometimes maybe help, but overall I think the economy is beyond anyone's control.
About the debt - I don't think any country is trying to reduce debt to zero - and the US isn't alone with a high debt to GDP ratio. The US is up there with the EU (collectively), Canada, many other countries, while Japan tops the list. I'm not saying it's not a problem (or can't become one), but the US isn't alone in terms great quantities of debt.
Note that sovereign defaults are common, I think they've occurred about once per year over the past 100 years. Not that it's a good thing or that I want to see it happen, but it's not a disaster either.
Right now, I think all economies are suffering due to COVID-19, or more specifically, what governments have done in reaction to COVID-19. The US economy was really strong (in terms of GDP, unemployment, etc.) until that happened. I agree with you 100% on military spending but I don't think any president will come around who will make significant cuts.