The whole concept of a "nuclear wasteland" was derived from Cold War-era anti-nuclear propaganda, not from reality. Likewise, the authors of the original "nuclear winter" paper later admitted that they had dramatized their results by focusing on worst-case scenarios rather than likely outcomes because of the perceived possibility of Reagan launching a first strike. In a Cold War context, if there is a big green machine in Germany, everyone knows which way to point their nukes. If not, the bulk of the French force de dissuasion is pre-strategic and only their submarines, which were not MIRV-capable before the late 1980s and early 1990s, could conceivably reach the US.
Without the Soviet Union involved I don't see any other nuclear power having enough force to leave the US as a 'nuclear wasteland (Unless the US launches against itself) The other powers could cause some heavy damage and there might be some areas that are a wasteland but I can't see a broad swath of the U.S. as a wasteland in such an attack. On the other hand once the US launched, even holding back a reasonable force to keep the USSR in check, any other nuclear power would end up as a smoking glowing hole in the ground.
