I know that the US was already very powerful before WW2, but from everything I've read, it makes it sound like a lot of the US's growth in the last 75 years can he owed to the productivity of WW2. Our infrastructure was intact and we were the ones who could reliably produce goods without threat. While Europe was destroyed, the US was able to thrive (not a bad things or anything.)
This question has a huge scope, so I will attempt to cover maybe one angle.
I would say yes, the US is what it is today largely because of WWII. Let's just look at the depression leading into it: Here you cans see unemployment from 1930-45. Notice in 1937 (after a decrease) there was a spike in unemployment, which was caused by FDR's decision to lighten up on statist policies. This decision was made because of huge opposition from the right against FDR's move away from Laissez-Fare economics (liberty league). However, the spike indicates that even the New Deal was only a treatment, not a cure, to the Great Depression. Without the treatment, the economy would just become sick again.
Now, notice that WWII, which started in 1939, brought about a decrease in unemployment to acceptable levels. If you use this as an indicator of the economy's health, then WWII saved the US from the economic disaster it was in. Thus, through WWII the US could put the depression in the past and move to a brighter future. This is part of it. Now as you mentioned, the US didn't face infrastructure damage like the other powers, and I would agree that this put them at an advantage. Additionally, in 1943, during the Quebec conference, there was an anglo-american agreement to work on the bomb (manhattan project) in the US. Britain would send their minds and the US would host (adding their own minds as well). Because the US hosted, they would get access to the bomb by Potsdam (conference) in the summer of 1945. So through that bomb we were now ahead of every country militarily, and because of the pond between Europe and the US, the US was stable economically, even thriving. Thus, if the world was in a 100m dash, the US definitely got a 10m head start.
However, I would caution you not to ignore other important aspects of history. As I said, this question has a huge scope, and where we are today is also largely, maybe even primarily, dependent on the competition of the Cold War and our actions in post WWII history. Like I said, we got a head start, but a head start doesn't ensure the win. In other words, WWII was a platform, but to get where we are/were afterwards we still had to do plenty of building on top of that platform
