Why Are We To Keep Peace With Jerusalem?

By we you mean, the U.S. ?  Why did the Pope's declare 2 holy wars (the Crusades) to rid the Holy Land of the Muslims?  Israel will always be a focal point in world affairs for one simple reason.  It is the Holy Land.  Whether you choose to believe it or not, whether you choose to accept it or not is irrelevant.  What is relevant is that the rest of the world does. We keep peace with Jerusalem because our country is predominately Christian not to mention a lot of Israel's descendants live here in the U.S. And hold a lot of influential positions in our society and government. I choose to be on God's side. Peace with Jerusalem?  Definitely YES!

The bible says those that bless israel will be blessed. Why? Because it was written by people that wanted their land to be blessed, duh!  No god wrote it.

By "We", towards which nation/religion are you talking about?
Since Jerusalem is not that much rich in minerals, oil, gold etc, We can be sure that Jerusalem is having its important because of religious importance. And, that importance is not in just one religion but among world's largest religions. The followers of both religion have their own views about Jerusalem and It is causing a clash among both religions thus causing violence.