Also interesting to contemplate the influence of WW2 in that fact. I think I generally hear that WW2 was a big booster of economic growth, so how long would it have taken without the war?
A glib way of answering this is to look at how much of U.S. GDP went to military spending. It was extremely high during the war and has remained at a higher average level ever since - thus Eisenhower's "military-industrial complex" remarks at the end of his term.
Minus that spending, it's not clear what would have happened, since we never had a return to the old status quo. The military investments of the war motivated the early development of Silicon Valley - thus, we'd be looking at a present day where "somewhere else" might have gained the tech hub crown.
That said, the current moment is one where the premises could change again. China has a strong and growing influence in the world, just as the U.S. did coming into the Depression. The particular circumstances differ, but a broad "cycle of empire" is one way to interpret things.
I think it's a great example of why it's important to try to not judge history. The complications in this one scenario are just so fascinating, yet it's important to resist trying to tie it up in a neat bow.