Israel - Friend or Foe ?

It occurs to me to wonder just what the criteria are for identifying another nation as a 'friend and ally'. I would think an ally would be called upon to assist in time of war. What is Israel's contribution to this 'alliance ' ?
Do we have military bases in Israel ? Is there a battalion or two of Israeli soldiers in Afghanistan ? Are they supplying war materiel to the front ?
Treating our wounded ?
From where I'm sitting, it appears that Israel may be as much of a threat to US security as an ally. The Arab world would have much less reason to harbor hatred toward the US were it not for our constant meddling in the affairs of the Middle East, centered around the presence of Israel.