I'm at best vague on the topology and geology of Berlin... but isn't it *really* flat and basically swampland? A nuke going of in Berlin'46 would spread the damage far and wide, but not deep. I suppose it'd be mostly reheating the ashes by that point, unless - somehow - Berlin had been spared firebombing in that timeline, as Hiroshima and Nagasaki had been. Were Berlin nuked and my understanding of the place is more or less correct... it would probably turn into a *really* verdant garden really fast. Flowers popped up overnight in Hiroshima, IIRC.
If the main difference in the timelines is the Germans spent less on the V-2 and more on FW-190's, the outcome might be some slight extension of the war. If they held on long enough to catch a nuke, I'm not sure that Berlin would be an effective target since it was already pretty well bombed, but doubtless some site could be found. So *that* might be one of the biggest post-war differences wrought by a lack of wunderwaffe... the atom bomb going off over some German military sites rather than Japanese. This would *probably* give the destruction more publicity as what happened to Europeans seemed to get more press than what happened to Asians.
Lack of wunderwaffen *might* have led to one of those utopian visions of a-bombs being banned, or handed over to some alternate version of the United Nations, or the Soviets getting the bomb faster/slower or the anti-nuclear movement coming on stronger. Conversely, nuking the bejeebers out of the people who brought about the Holocaust might actually make a-bombs look *better.*
Extra conversely: if the war lasted long enough that nuking Germany was an option, the argument about using the A-bomb on cities might have gone differently. Since, this being the 40's, American military leaders might have been slightly less sanguine about wiping out Europeans than Japanese. And if that had happened, and the war ended without nukes being used, or used in some non-city-destroying demonstration... World War III might well have occured by the end of the 50's. What seemed to change after WWII was that the world saw just how horrific an atomic attack was and that spooked the various leaders just enough to keep world wars at bay. Without the examples of Hiroshima and Nagasaki, though, some idiot might have concluded that an atomic war wouldn't be so bad.
