So we just need a nice all encompassing global conflict again that largely leaves the American industrial base alone and then when it is the only one standing there can be another growth in the American middle class.
Italian Economic Miracle: https://en.m.wikipedia.org/wiki/Italian_economic_miracle
Japanese Economic Miracle: https://en.m.wikipedia.org/wiki/Japanese_economic_miracle
Spanish Miracle: https://en.m.wikipedia.org/wiki/Spanish_miracle
Miracle on the Rhine: https://en.m.wikipedia.org/wiki/Wirtschaftswunder
In all of these cases real incomes grew enormously. Yes, a big part of that was starting from a low base after the destruction of WWII. But I'd argue it was also a strong consequence of the technology of the time: the was an explosion in consumer goods enabled by new tech, but companies still needed lots of employees to create these products. In the past ~25 years I believe tech has instead allowed more wealth to accrue to a smaller and smaller subset of people.