What was wrong with Zero's explanation? He just listed the 2 reasons the United States finally declared war on Germany.
As the most powerful country on earth, I'm pretty sure they could acquire the required territory from which to launch an attack.
There is no way the Germans could have invaded the North American continent. I don't know what territory the Germans could have acquired to launch attacks in the Western hemisphere until bombers could travel all the way and back. And this is getting ahead of ourselves because the Germans were still stuck on Step 1 of making a nuclear bomb.
None of us can be sure about how long it would've taken the Nazis to get a working nuclear bomb but what we do know is the US smuggled Nazi scientists out of the country so they could avoid trial & work for the US on their various programs.
That's true. The Nazis' scienctists were advanced in terms of missile/rocket capacities. However, this doesn't have any relation to their nuclear program.
As for the morality question, not everybody who worked for the Nazis was necessarily a war criminal. These scientists weren't Himmler or Goerin. The entire society was mobilized for the war effort. They were fighting for the wrong side, but that doesn't make them guilty of the Nazis' war crimes either.