Well, it's not quite as simple as walking away from the situation...
Our support for Israel as a nation state goes back to May 14, 1948. On the day that the British Mandate over Palestine expired, the Declaration of the Establishment of the State of Israel was signed by the National Council that had gathered in Tel Aviv. The Declaration went into effect at midnight and, 11 minutes later, President Truman (against various sources of advice) responded by officially recognizing Israel as a nation state. President Truman felt that the Jews deserved a sanctuary, of sorts, after the Holocaust. In addition, he believed that the creation of the State would help to foster stability in the Middle East.
Israel is a democracy. A parliamentary democracy, but a democracy nonetheless. The United States has always been of the mind that it would support, in good faith, countries that share, even at a very basic level, the same democratic values as we do. Israel also shares other ideals with the United States - more specifically (and more relevant to a very hot topic in the U.S. now) a very staunch anti-terrorism view. Let's face it, not too many countries can claim to be more of a victim of terrorism than Israel.
We cannot simply "step away" from the situation in Israel. To do so, I believe, would discredit the United States and always raise questions, in the minds of our allies, as to our loyalty and dedication to the very support we pledge. It would show weakness and vulnerability in a time when strength and might are the images that the United States wants to portray. I understand that our continued friendship with Israel puts us at risk for continued terrorist acts, and I'm not unsympathetic to this. However, as an American citizen, I would rather be hated for being unwavering in my values and support of our friends, than be hated for being undependable and wishy-washy on the world stage (hey, France - any of this ringing a bell?).
Israel is, of course, our best friend in the Middle East - we provide foreign aid to them (which is less than one-half of 1% of the federal budget, by the way) and they buy a schload of stuff (military and otherwise) from us. It's a symbiotic relationship where we also trade intelligence information. ha-Mossad le-Modiin ule-Tafkidim Meyuhadim
(The Institute for Intelligence and Special Tasks) is our greatest source of information in the Middle East. Without them, we would be suffering at the hands of terrorists much more than we already have been. Without us, they, most certainly, would have been wiped off of the map long ago.
So, with all that being said (yeah, I know - it's a bit of a novelette), again I say, God bless our troops around the world - may today be the day you finally get to come home.