Honestly, the whole, let a bunch of innocent people die and a genocidal dictator take over just seems stupid to me. First of all, ignoring the problem "harder" is almost never the solution to the problem. Tell the starving kids in Africa that "ignoring harder" is the solution, or pretty much anyone suffering. If it worked, most the problems in the world wouldn't exist.
The second issue is, you're incredibly naive and short sighted if you think this will never found a way to blow back on America or the rest of the world. It's not as if militants who have an undying hatred of western culture and attacked us more or less unprovoked were going to stop their genocidal campaigns, lay down their arms, and stop invading their neighbors if we had only ignored them. We would have eventually been dragged into the conflict considering that no-one is happy JUST with Choslovakia and Belgium, and Poland etc., only it we would have been hit a lot worse than a few trains or buildings being blown up; we waited for another pearl harbor, and it happened, where we finally got attacked directly, and people still think we shouldn't have gotten involved. Ignoring WMD's, Iraq had the 5th largest military in the time with mostly modern Russian equipment (for the time), behind only the U.S., North Korea, China, and Russia. Bigger than the UK, France, Germany, Pakistan, and so on. Iran also had a huge military, with, largely Russian military equipment. Had they fought another war, had they just been allowed to invade Kuwait, Saudi Arabia, Israel, the war would have been so devastating it would have consumed the middle east, and then moved on to Europe which, is right next to the middle east, and then the world. They wouldn't have just stopped killing the Kurds in their own country, they would have moved on and on and on trying to take over their neighbors. Iraq would have never been happy with just Kuwait, just as Hitler would have never been happy just with Belgium.
Then, let's throw in WMD's. Iraq had them, as well as 500 tons of Uranium. Iran would have had nuclear weapons, if we hadn't of bombed their reactors, like we did with Iraq. Pakistan definitely has them, and Israel probably has them. Iran has a military of about 2.4 million people; that's about 30% of Israel's population. Because not every man, woman and child can pick up a gun and fight in Israel, there likely would at least be a 100% annihilation rate of Israeli citizens. The Basij has over 11 million people, which is some 30% MORE than Israeli's entire population, or 70% more when combined with their standing military. Threatened with total annihilation, you can bet Israel would have resorted to their most powerful weapons, and once the nukes start to fly, it's pretty bye bye for the rest of the world.
Iraq WAS threatening war on Israel, and Iran, and Saudi Arabia, and pretty much everyone else before we invaded.
WWIII was at out doorstep with what was developing over there. Had it been allowed to continue on it's path, Armageddon would have been a surefire hting. Now, our worst threat is a few thousand idiots in sandals robbing oil wells that they can barely sell the oil out of, a few banks, with Ak-47's? Even if we're going to pretend Bush made them somehow, which is very stupid, I'd take that over the Saddam regime which killed hundreds of thousands of people in mass genocide, the mass graves of which are still being found, and the development of nuclear weapons which would have existed and, AT LEAST, the resulting conventional wars, had we not have intervened so many times.
I don't like having to spend money on the war, but it's not as if these problems will simply go away just because we ignore them. We are a part of the world, and thus effected by it. What happens in it, effects us. And thus, eventually, this problem would have come back to bite us in the ass much worse if it was just left to fester. If anything, we should have gotten involved sooner, before it turned into this shitstorm.