Not just Unit 731, but a lot of America's rocketry experience was imported wholesale from Nazi Germany. We are talking 1500 scientists, technicians and engineers (https://en.wikipedia.org/wiki/Operation_Paperclip) including Wernher Von Braun, the designer of the V2. Indeed , Von Braun had been advocating space flight since the very beginning- all the evidence suggests that his tryst with the Nazi weapons program, was merely in order to further his ambitions for human space flight.

Where would America be in the space race, had they not done this? I think in hindsight, it was a pretty clever decision - these people were probably the most valuable war bounty America got out of the whole deal.