Been hearing "unsustainable" for a long time. I believed it wholeheartedly for a while. Sure, we will have recessions again, perhaps we're in one presently, but do you think the USA is going to somehow collapse? It will likely see a gradual decline in living standards, I agree, but you are overlooking how bad the 70s were economically, when the Baby Boomers were in their 20s and 30s.
That's the thing though, we shouldn't be seeing a decline in living standards. Technology, productivity, efficiency are all up dramatically. We just have an oligarchic ruling class sucking up all the difference.