I think from a alternate world POD point of view the case could easily be made that the outcome of the Arab Israeli War of 1948 (other names for this conflict / war / whatever are available) could easily have been different if for example the Arab forces had been better trained or the five Arab countries involved were less self-serving . However, I think Chabon's idea is that this is supposed to be a grand sweep of history, which I don't really think fits the facts. It was all very messy and contingent and my gut feeling is that most people have a sort of folk-history view of it which bears little relation to reality.
Also, Chabon breaks alternate reality rule 1 - no cold war, no computer revolution, no mobile phones, shoyfer or otherwise.
OK, I shall shut up about this one, though I reserve the right to quote from the Glubb biography when I start reading it.
(I am looking forward to the random drive-by search driven comments on this one :-))
[At least it was better than the Nancy Kress novella that won the Nebula, the only other winner which I have knowingly read, which struck me very much as a typical Isaac Astral's SF by numbers story]