Right now I doubt Israel would have such an easy task were they to take on the Arab world. And while they do retain a friendship with Israel, the U.S. has over 2.5 million muslims in their country, which could get pretty angry were they to be involved in what will certainly be perceived as a religious war.
Last bit is especially true, but frankly the US has turned the War on Terror into more or less a religious war as it is. SOMEone is going to get offended. It's a very difficult situation.