I would like to think that cooler heads would have prevailed and done a bit of analysis before a knee jerk start to WWIII. Still, one never knows, and it's funny that one talking head in Russia did indeed blame the US for the event.
The real teller is that a nuclear weapon re-entry vehicle contrail would not have been that flamboyant since they are very small, even though the blast that I've seen sure reminds me of a small nuke.