I think you're missing half of #1... While we did have to fight the Cold War, which led to much progress on a technological front, the US also had the advantag

I think you're missing half of #1... While we did have to fight the Cold War, which led to much progress on a technological front, the US also had the advantage of reduced competition from previous world powers (UK, Germany, France, Japan, etc) which had been destroyed by WWII. The Communists gave us focus. The end state of WWII provided the economic ability to put that focus to good use. Or something like that. But, I do agree that the lack of a single unifying enemy is a problem when it comes to motivating society as a unit. It feels like we're more likely to be destroyed (as a nation) from internal factors than external, and that's not good.