My Occam's Razor is, "problems are hard." Besides, if you believe the US empire is failing overall, that doesn't seem compatible with every individual system within it operating as intended despite appearing to be failing by all observable metrics.
You can't print money to pay for everything. Who's going to accept that money in exchange for goods and services? Aquaman? If somebody told you that the government can print money forever, they were lying (or at least had never heard of Zimbabwe).
Perhaps we can split "purpose" into "intended purpose" and "emergent purpose," that is, the purpose that can be derived retroarctively from observing its function and modelling the system as an agent unto itself. For instance, I think you're conflating the intended purpose of the War on Drugs with its emergent purpose -- can you really deny that it was created with the intention of obliterating drugs? Seems conspiratorial to me, given the breadth of support the program had. But I could say that its emergent purpose became incarcerating black people due to flawed design and lack of oversight. And of course, this flawed design and lack of oversight was permitted to exist due to institutional racism in the meta layer (society and the government overall).