What does Israel contribute to the U.S. that allows the U.S to defend it at all costs?

Since it was created over 60 years ago the United States has defended Israel on almost every front. What is the cause for this, since it has only led to widespread destabilization and continous conflict in the middle east? I could, possibly, understand if Israel offered the United States some sort of valuable commodity in return for this unfettering aliance, but it has nothing that contributes to our so called "way of life" that George Bush proclaims is his justification for his republican (insanity) agenda around the world; one that endangers America and Americans more so than any other single event in America's History as a nation.