If the Nazis had access to Extraterrestrial Technology

Those rockets were ahead of their time and the basic design brought man to the moon. That was quite a jump of technology. Nobody had the technology to build laser rays at the time. Have to work with the tools you have. Germany would've won the war if they had more time but it was too late when the rockets were designed. Their fate was sealed.

As much as i like to dismiss the theory, i do like an idea that lies behind it.
Even though Ancient Aliens did not actually take this approach, this is merely me thinking out loud.

But suppose the Aliens somehow knew that Hitler was losing it, therefore eventually losing the war (assuming the Aliens mean well for the greater good). Giving them this technology instead of the winning Allies might have caused the Americans to have respect for the technology and implement it like our current state of affairs.
If Aliens had decided to support USA and gave them the power to influence the events even more (aside from the addition of Aliens to the equation), USA might have gotten even more powerful and hungry than it is today, which could have disastrous results on its own.

But yeah, then again, why jet propulsion? Its not like we had no idea of the principle concept. The science of aerodynamics and propulsion would eventually bring us to this anyway. Balloons already existed, it would take only one person to see the link between the way a balloon propels itself and the implementation of this concept using fuel in rockets.
And why choose to intervene to begin with, especially since jet propulsion is eventually not really a big leap in technological advancement, it came at a crucial moment but it didnt make the Germans win the war either.
Rockets got us to space, but that doesnt mean that we wouldnt end up there anyway, we have always dreamt of the impossible, breaking records and extending limits, besides rockets get you nowhere on the Universal scale, mass and speed being the main obstacle.
Stories about "Die Glocke" already get a bit "out there" since no such device has been found. Besides it would make the Aliens appear mean-spirited by dropping knowledge bombs on the Germans only, also, if they did not mean well, how could they lose to us? Were not that amazing or something. Indeed. you have to wonder...

It's about reverse engineering...

I believe there was a discussion on the show talking about how it would depend on what their technology was based on...As to what we could come up with. If they had technology similar to what we already had then we could quickly advance. If it was something completely different than the things we already knew or were familiar with, then it would be very difficult to do anything with it.

We had Automobiles, and Aircraft that required fuel, chemicals that get ignited to create combustion that is used to propel an object. Rockets. They also require fuel, chemicals that get ignited to create combustion that is used to propel an object. Jets and Rockets are just a more advanced form of Combustion Technology... It was rather easy to make the advancement from one to another.

While we knew that is was Mathematically and theoretically possible for such things, like Antigravity, Faster Than Light Travel, Time Travel, ETC... to exist BEFORE WWII... We did not have anything like it. The technology was far too different to understand and replicate in just a few years, or even decades... And we still don't even have such technologies.