I had seen the graphic long ago, but could not remember where I had seen it. I did remember the final outcome, which was quite brilliant. Vietnam, having defeated the US, was to face Afghanistan, having defeated the Soviet Union. That was the punchline.
The good news is that I was contacted yesterday by a scholar who was looking for the original ... and then contacted again when he found it. It was in Spy magazine and then re-posted at the Atlantic!
My memory was not all that far off:
Given how history really played out--that Nazi Germany was defeated by the USSR, I think I prefer US vs Japan and USSR vs. Germany. Otherwise, still quite good.
Anyhow, big H/T to AM for letting know where we can find this wonderful graphic!