Luftwaffe over America

Hi Everyone,
I bought an interesting book today that I have not yet read, but that I plan to read. It's about the German program to build long range bombers by Messerschmitt (e.g. Me-264), BV, Horton, etc. that would reach across the Atlantic and hit American cities.

Perhaps the main reason this did not happen is that American and British bombers were destroying German production facilities.

But let's take all of that out and assume that the Germans had had the full resources to build as many Amerika bombers as they wanted, then...

1. What would they have gained?
2. Would they have had any impact?
3. What would have been the opportunity cost in pouring resources into such bombers?
4. Would it have shortened the war or affected the course of the war?
5. How technically feasible would this have been?

The book title is "Luftwaffe over America". And one of the key premises which I omitted is that Russia would have been conquered and that the Luftwaffe would have had access to unlimited fuel and resources (meaning raw materials for manufacturing, ostensibly). I'm fine with using this as a premise for the purpose of this discussion.

While vengeance weapons might have been good for the Nazis, it's hard to see why they would have tried to develop so many different long range bombers to deliver one or two atomic bombs.

I don't think there would have been American aircraft to intercept them historically, but I would assume that if the Germans had gotten something realistically capable, then the US would have made proper arrangements - like parking a carrier off shore New York.

If the idea was to have nuclear attack, then why not just sail two Type XXIII or XXIII u-boats a few miles away from NYC, load the 1st crew on the second sub, then set the first sub on autopilot with a device on autotimer, then set it to go?
That would have been easier than mass producing bombers.
So my sense is that the primary objective would have been to have tried a sustained Battle of Britain type Battle of America.
Narayan