Israel didn't fall
In the book "World War Z" (on which the film was supposedly based), it's pretty clear that Israel abandoned Jersualem as indefensible.
"A lot of Israelis had to watch their houses bulldozed in order to make
way for those fortified, self-sufficient residential compounds. Al
Quds [JERUSALEM], I believe that was the final straw. The Coalition
Government decided that it was the one major weak point, too large to
control and a hole that led right into the heart of Israel. They not
only evacuated the city, but the entire Nablus to Hebron corridor as
By the end of the book, there are several mentions of the Jewish "masada" model of walled cities being the way in which many countries organised themselves after the initial zombie assault.