No, the US didn't save the World single-handedly. The Soviets bled & bled, & did most of the fighting & killing in WWII - look up the combat stats anywhere. We provided a lot of industrial & agricultural muscle, & some troops - again, look @ the manpower the combatants put into the war, the percentage of KIA, WIA, captured, dead of disease & accident.
Western Europe, Japan, & eventually Eastern Europe & the Soviets more or less willingly followed our lead in movies, popular music, consumer goods. But it was often against the sensibilities of the elites & government functionaries. The developed world has prospered, on the whole. Now we're coming up on pollution & environmental contamination, limits to fresh water, arable land, barriers to further expansion of food sources. Yes, the rate of extreme poverty in the World has fallen over the last few decades. It's not clear if we can sustain that, nor for how far into the future.
These are tangible goods - if we can sustain the trend lines. If not, it will be the biggest crash in human history. We can hope that there are technological or biological fixes that we can apply. & that the cures themselves won't entail further & worse problems.
