While the USA performs D-day, with an estimated casualties of 4/5, and conquers Germany so that they can acquire the Nazi flying saucer technology before the Soviet Union, people begin to feel worried about the alien invasion, witnessed by reports of flying saucers from all over Europe in the 40s, and later in the USA after Operation paperclip in 1945.
Unidentified Flying Object tells the story of how Nazi Germany, as an economy that was boosted by the rest of Westphalia to be a bulwark against the USSR, managed to construct Nikola Tesla's flying saucer technology similar to how airplanes and helicopters were once constructed for the first time, how the USA raided Germany to acquire it, and how people began to believe they were invaded by aliens. The movie shows both sides of the story, and focuses a lot on how people start to believe they are invaded by aliens, because that is hilarious.
Here is Edgar Mitchell, astronaut from Apollo 14, who firmly believes that his government has covered up a crashed alien flying saucer.