It may be a "limited" nuclear war
Instead of the Cold War with just about everywhere getting hit or affected by drifting radiation, we may have a limited nuclear attack. Not that it makes things better, but World War 3 may not be quite what was once predicted.
I can forsee Iran and Israel nuking each other and much of the Middle East while the US and other oil-hungry superpowers wait for the radioactive dust to settle to move in.
Would France get involved?
Would North Korea strike South Korea and/or Japan during the Middle East melee?
If this happens, watch the US become a martial law until further notice nation.