DG OT < sorry folks, but Alternate History is such an interesting topic
>
Nazi Germany would have faced the same issue as Russia / China etc do now:
The US is so geographically vast that it would take hundreds of Hiroshima-size nukes to really hammer it down.
1-2 destroyed cities, or more likely a near / far miss, might have just stirred up the US to action, as Pearl Harbour did
Also, after a few years of war, the UK was nearly on its knees, whereas US was booming and far more able to cope.
With a federal stucture, the US is far more decentralised than the UK, which reduces the effects of a decapitation strike
In the early days Germany, like the US, would have only had 3-4 bombs, so they would want a secure delivery system, not an iffy one
and they would want to efficiently end the war, not just make a big show
The UK, even then, could have been effectively beaten by 2-3 bombs dropped by air, or maybe missiles - the V2 may have been the precursor
At least enough for the surviving govt to sue for peace
That would have ended the Western front of the European War - and the US involvement - and let Germany concentrate on the Eastern Front
Hitler hoped early in WW2 that British fascists, including in the aristocracy and royalty, would take over the govt and agree to peace
However, that hope ended once Churchill got firmly into power
Hitler showed no reluctance to slaughter umpteen 1000s in the London Blitz and Coventry etc
- he realised Britain would have to be really hammered by the war before the Uk fascists would have another chance at taking over.
So imo would have taken the easiest opportunity to win the war by knocking out the far more vulnerable UK, rather than the US.