Poland in the 1970s produced around a tenth of US 2013 per capita GDP from nationalised heavy industries and peasant farming, under a system that was at least theoretically Marxist. What makes you think the US is headed in that direction?
I'm not sure which US metrics the peaked in 1970 either?
There's not much to say about the 1st paragraph other than observation and extrapolation of trends. Not a change of direction, rather BAU + time. I do agree with your observation that we have different PR campaigns, which is a correct and valid point. Poland had a mostly centrally controlled economy pretending to be Marxist, and we have a mostly centrally controlled economy pretending to be capitalist, wildly different PR but same operation conditions, and in practice the operating conditions are more important than the PR.
The metrics request is a good one, having seen the graphs I'm certain of peak conventional domestic oil production, peak median inflation adjusted real world income, and peak housing affordability. I'm pretty sure of local minimum of parasitic services (FIRE sector etc) and a local maxima of educational affordability and a couple I suspect but have no proof of at this time like a peak in the metric of quantity/quality of health care divided by its cost and also social class mobility has statistically ended other than in a downward direction where it has expanded a lot.
I'm not sure which US metrics the peaked in 1970 either?