Well there were the Junkers JU 290 and 390, and the Messerschmidt ME 264 V1-3.
http://www.militaryfactory.com/image...ircraft_id=759
Along with the ****e-Wulf FW 200 all four-engined bombers, however there would not have been much chances - even if it would have bombed the US with whatever bomb, it would never have brought he US to an armistice with that action.
Also, the german nuclear project was hindered by a never openly outspoken agreement of the partaking scientists, they just did not want to develop that thing for Hitler. Heisenberg writes about it in his autobiography.
Certainly, had von Braun been in that project ...
edit: ****e-Wulf ? lol PC goes a bit far
Greetings,
Catfish