As someone chewing their way through a WW2 history book (Neptune's Inferno) at the moment: I think the presence of external enemies mattered hugely. As it did during the cold war. Those in charge actually needed the effort and bodies of the public, for material war-fighting purposes. That drove nation-building solidarity efforts.

It also forced a certain amount of pragmatism; useless ideologues whose plans failed could get replaced rather than promoted, and at the middle ranks there was even the possibility of them getting themselves killed.

America in the present day is consumed with imaginary internal enemies, which is why it's deploying troops on the streets.