To deal with a few of your points in the clearest way I can; though, with respect, I think you indulge over optimistically in Wish politics, wish economics and wish-science. (my own terminology)
This or that — -”needs to be done” (wish politics/economics/science) People do not submit willingly to totalitarianism — -but that’s what it would mean, as I pointed out in a previous response. Wanting people to submit to logic and common sense will not make it happen, because our genetic forces will not allow it.
Though I admit the German people will readily see sense more easily than Americans and a few others. (We idiot Brits leaving the EU is a case in point)
“A moderate change in our democratic system”, is certainly wish politics for most of the world. Look at South Africa right now — -gearing up to take back white farms, making starvation and collapse certain there. Venezuela has done equally crazy stuff re “socialist dogma”.
FDR’s New Deal was put in motion only through the availability of virtually free oil, and cheap machinery to use it in. He put thousands to work constructing infrastructure, but by 1939/40 this momentum was petering out….as infrastructure is built, it must have input/usage of more and more energy (fossil fuels and people) to keep it viable. The Hoover dam (and others) needed consumers.
The Grand Coulee dam was a typical case in point, it was a white elephant until WW2 created the need for aluminium on a colossal scale.
Hitler was doing the same thing in the 30s as FDR — maybe on a smaller acale — -by putting people to work making ‘stuff’. Both were ultimately unsustainable — -both indulged in ‘wish economics’. The end result for Germany and the USA was conflict. In the 30s/40s, the doctrine was the same as now — infinite energy/progress/ supremacy making war inevitable.
“National Socialism” and “National Capitalism” arrived at the same economic cliff edge, separated by a few decades.
If National Socialsm had prevailed in the 40s, then Hitler’s economic/political system would have arrived at the same finite conclusion, and would have been in the same state of denial about it.
As I think it will be for many ideologies in denial of what is actually going on, which is my underlying reason for thinking civil war in the USA is ultimately inevitable. (mutual denial of reality) by entrenched collective stupidity. Watching Trump supporters sounding off confirms that I think.
In the event, it was Hitler who solved FDR’s “great depression” by kicking off WW2, thus creating a massive demand economy that ran on until 1970.
Why 1970? That was the year the USA went into oil deficit from oil surplus.
Global economic systems in general have been volatile since then, one way or another.