I think it's obvious that the Soviet Union was a vastly greater threat to the U.S. than Islamic terrorism will ever be. But some readers don't agree; in their view, the practice of Mutually Assured Destruction (MAD) meant that, in practice, the Cold War was never going to turn hot.
I don't deny that the threat of mutual annihilation reduced the probability of an all-out war between the U.S. and the U.S.S.R. But I am far from convinced that it reduced the risk to anything like 0%. After all, there were a number of near misses and false alarms; and in any case, revolutionary Communists are notorious risk-takers.
Imagine this thought experiment: Suppose we "re-ran" world history from 1945 to 1991 a hundred times. Put hindsight bias aside. How often would we approximately get the peaceful resolution that actually happened? How often would get get something much worse? And how often would we get a full-blown nuclear war?