When I was rewatching Phineas and Ferb on Disney+, I came across a problem. How did the ocelot-raised villain become so wise in the ways of science? Heinz Doofenshmirtz was born in post-war Germany and it's truly a miracle that he was able to make it out of Soviet occupied lands. Seeing as his parents were "abusive" one would be led to think that his parents would've turned him into the KGB. Well I believe there's something going on behind the scenes.
We all know that post-WWII the US government brought over Nazi scientists to work on rockets. According to the Phineas and Ferb Wiki, Heinz was about 65(average as the show stated different ages) when the show began. Since the show takes place in 2008 it is safe to assume he was born in 1943, before the end of the war. This explains why his parents were not present at his birth, they were off defending their country.
Doofenshmirtz grew up in post war East-Germany in a town called Gimmelschtump. This is shown to be in Drusselstein, a state bordering the Baltic Sea. When he was around 6, his parents were so poor that Mr Doofenshmirtz(Heinz's Father) had his gnome repossessed. They were so poor because the Soviets were oppressing their former enemies. From an early age Heinz's parents saw his talent for science and did their best to keep the Soviet overlords from learning of him. When he reached 16 his parents saw an opportunity to save him and shipped him off to America. This allowed him to learn how to develop complex machines and come under the notice of OWCA. The Organization began keeping tabs on the Operation Paperclip scientists, just in case they still harbored Nazi sympathies. As we see later in the show, most villains fought by OWCA agents were scientists, many of whom were of Eastern European descent. Perhaps OWCA was the US government cleaning up their crimes and to do so they used agents who could never reveal the truth(hence the animals).
So this explains why the doctor found his way to America. But what isn't addressed is how America found out about the Doofenshmirtzes. This can be addressed by simple inheritance. Heinz had to get his love of science from somewhere, his father. Mr. Doofenshmirtz spent years pushing Heinz away, hoping to spare him from the horrors of Hitler's regime. Mr. Doofenshmirtz was most likely a high-ranking member of Hitler's scientists. This explains why he always had people over for dinners and made Heinz stay outside. To keep him safe. Mr Doofenshmirtz, however; was still a fanatic and when his second, more desirable son was born, he willingly gave him to the state. This left Heinz to continue to feel dejected; which would make the separation much easier for both of them.
With this evidence I believe we can build a timeline. Once Hitler rises to power, Mr. Doofenshmirtz joins the party and rises in the ranks. Doofenshmirtz then perpetrates Kristallnacht and continues work. Eventually he begins work on rockets and has a son. His son does not fit into what the party deems "pure" so he pretends to ostracize him while secretly teaching him science. The war ends and they find themselves under Soviet rule. In order to save him, Mr. Doofenshmirtz sends Heinz to the US. Heinz then begins work for NASA along with other German scientists. Operation Paperclip is shut down and the scientists begin independent work. The US establishes OWCA to keep watch over the scientists. From here Dr Doofenshmirtz believes his father to have hated him and vows revenge. Things play out until 2008 when the show begins.
This explains Dr. Doofenshmirtz's desire for conquest and parts of his inner anger. The US was all too happy to have another German scientist, especially one stolen from Soviet lands. We know from history that many other Nazis came to America. And many settled in the Tri-State Area, conveniently that is where Dr Doof lives as well. The evidence is too much for me to deny, Dr. Doofenshmirtz was certainly brought over as a part of Operation Paper Clip. He was only scrubbed from even the CIA's records due to his work with OWCA once the other Nazis were defeated.