Went around Kennedy some years ago on the all-day visitor excursion. The elderly tour guide had worked there all his career and had fascinating personal experiences going back to these early days, which got a couple of us asking him for more and more reminiscences.
He said that Werner von Braun, and his German colleagues, would be in the concrete bunker watching it all. When there was a malfunction they would start gabbling in high speed German, with one another, gesturing, scribbling designs, etc, which the launch director and others could not understand until they were persuaded to calm down and start the debriefing in English.
Von Braun had of course done all this before getting the V2 launches which attacked Britain in WW2 going, and had been spirited off to the US in 1945 and given a prominent position on the early rocket team. At the end of our tour I asked our guide how the US would have felt if the designers of the 9/11 attack had been taken to Britain and given significant positions in the UK government. He said it wasn't the first time such a question had been asked.