Come on, building and rebuilding other country's economies is a boon to the local economy, particularly when that other country is footing the bill. That's literally why the US was on top starting at the end of WWII. Not everything the Soviets were doing in the 70s is the reason for their downfall.
I'm sure it helped, but the U.S. was already by far the dominant power before that economic activity.
At the end of WWII, the U.S. produced half of the world's GDP, a staggering number. It was the only advanced country which was physically untouched by the war, it had troops stationed throughout Europe and the Pacific, and it was the only country with nuclear weapons.
It says a lot, IMHO, that the U.S. didn't pursue a global empire at that point.