If I remember Oppenheimer (who was one of the chief members of the Manhattan Project during the war, even though we became an avowed pacifist later leaving Teller to lead the way to its actual development in '48) said that if they had been just 6 months farther along after German capitulation he thinks the project may have continued. What a scary prospect that is. You have to wonder in the US had completed the development and used the weapon during the war would the Soviet program likewise been on an accelerated timetable after the war? What would the implications be of both having nukes before the end of the decade and nukes having already been used in war? Would it be a Pandora's Box? Or would the use of the weapon actual discourage further deployment?Anyone here heard of the Manhattan Project? It was a secret WWII American project to build a nuclear weapon, mostly intended to counter Nazi Germany. When the Reich fell, the project was cancelled, but the decision to cancel it was a close one, with a serious contingent arguing for continuing the project for use against Imperial Japan. If the project had been carried to fruition (it was technologically feasible, barely), it could have led to a much more violent, but shorter, end to the Pacific Theater. Nuke a few Japanese cities to force a surrender, type of thing. You still run into the problem of Nazi Germany's collapse cutting the European Theater short, but at least you make the Pacific Theater a bit less of an obvious target. Nuking your enemy into surrender is not exactly war film material.
Of course, deploying nuclear weapons in war is a pretty crappy way of getting anything done. But it's an interesting thought nonetheless.
As far as what this would have done in American cinema, I'd have to say I don't see it making the European Theater any more attractive. At best it would reduce the number of WWII films all together because of the reduction in material for inspiration without Downfall.