That's exactly the same question a lot of Americans asked about Hitler and Nazi Germany. What business was it of ours? If the Japs hadn't bombed us into WWII, it seems a pretty safe conclusion that Nazi Germany would have taken both Russia and Great Britain, as well as all of the Middle East and most of Africa. The Japs would have gotten China. Wouldn't that have been a lovely world map. And, can you doubt that once they solidified their positions, we would have been next, only with no allies at that point?
For precisely those reasons, western democracies have a long history of supporting one another. True, there is no power in the Middle East today that could replicate the nightmare above, but do you seriously doubt that one could arise? For many of the radicals over there, the re-unification of the Ottoman Empire is not an idle wish-- it's a goal. The right charismatic leader could make it a reality-- and the right charismatic leader could very well be whoever succeeds in driving the hated Jews into the ocean. Israel may be small, but it is a fulcrum for Arab rage. Think about it-- it's a tiny little country, occupying a tiny little piece of land, in a big, big Islamic world. What the heck is those people's problem? It's COMPLETELY irrational-- why does the rag-head world care about a few acres at its edge? I can tell you why-- because with brains and industry the Israelis have built a first world nation in one of the most inhospitable parts of the earth, showing up the rag-heads with all their oil money for the failures they are. The rag-heads can't BE Israel, so they have to destroy it. They feel the same way about us, by the way. (I'm using the term rag-head as a generic because it's not just Arabs, it's Persians, and lots of other Neanderthal tribes.)
For 50 years we followed a policy of containment of the Soviet Union's expansionist goals, and if you ask me, we're looking at at least another 50 containing islamic fundamentalism.
Those are the historical facts; look them up. We were not gung ho to die to liberate the concentration camps. We lost 300,000 in WWII (including an uncle of mine) and thats bad, but put next to the sacrifice of the Russians to defeat Hitler and it gives you pause. Russian civilians WERE the front lines; we never want American civilians to be the front line, but they were on 9/11. It took only 19 men from the enemy to kill 3,000. Its serious.