That's because they need some sort of human catastophe and Israel seems most likely to go that way. It's almost a lazy choice. At least when Heart of the Comet has a blasted Israel, it is because the fundie Christians, Jews and Muslims overcame their differences to realise that their real enemy was Liberalism, and the protagonist, Saul, wept over his memories of the burning Kibbutzim.

I like David Brin's alternative in Earth, where the Nuked country, only spoken of in whispers, is Switzerland.