The question as I see it is not whether or not we should “smash up Iraq.” We should do what advances our well-being. At the moment, getting at the terrorists is more important for our well-being than smashing up Iraq. Smashing up Iraq will not stop terrorist attacks now or in the future, even those with weapons of mass destruction. It might teach a lesson to other countries, but I believe the fate of the Taliban has done that. As far as I know, none of the countries that Steve mentions is supporting terrorism against the United States. On the contrary some of them are working (at least somewhat) with us against our common enemy, violent Islamists. Individuals in those countries, especially Saudi Arabia, may be sending money to terrorists or the institutions that nurture those who eventually become suicide bombers but, since these people don’t keep their money in those countries, smashing them will not necessarily stop the flow of money to the terrorists.
As for smashing countries in the Middle East, let Iraq serve as an example. We invade Iraq and take control. Then what do we do? If we pull out, who will keep control? Does anyone believe that the Iraqi opposition will be able to function as a government? Will the Europeans be up to it? The Turks could probably do it but it would not be pretty, since they would be likely to focus on a final solution to their Kurdish problem. Iran of course has geopolitical and religious interests in Iraq. Do we want the Iranians stepping in to the vacuum our departure creates? Anyone want the UN to take over? If we pull out, chaos is one likely result. If Afghanistan as a lawless home to anti-American Islamists turned into a big problem, Iraq post Saddam could be much worse. And if we stay? Do we want to occupy Iraq? That will create even more anti-American sentiment. The problem with this is that we need the cooperation of lots of countries around the world to handle al Qaeda (AQ). Creating mass anti-American sentiment in the Arab world is what AQ has been trying to do. Why should we help?
Saddam’s weapons are a serious problem, so serious that we may have to do whatever is necessary to take control of them. We should recognize, however, that doing so through military force is likely to create problems just as serious as those we would be trying to take care of.
The above of course is based on my typically pessimistic view of the world. Everything might work out. Post Saddam Iraq might quickly turn into a liberal democracy and start a chain reaction of liberal democratizing throughout the Arab world. Remember the effect of WWII on Germany and Japan? I think this happy outcome is unlikely. The Middle East today has almost nothing in common with Germany and Japan before WWII.
As for a strategy, I would suggest the following. First, we should recognize that we cannot exterminate Wahhabism, which is an idea. (Even if we could, it is not the only form of violent anti-American Islamic thought in the world.) We did not exterminate Marxism. It collapsed of its own contradictions. (Would the disappearance of the current Saudi regime have the same effect on Wahhabism that the collapse of the Soviet Union had on Marxism?) The same fate may overtake Wahhabism. In fact, in Egypt, where much of the Islamist (but not Wahabbist) thinking started, there are signs that people are turning away from violent Islamic views. Our strategy should encourage this. We should isolate the violent hard core, attack them (kill or capture them, whichever best serves our interests), strangle those that remain by depriving them of resources and develop some hedges in case isolating, attacking and strangling does not work or, which is likely, work completely.
To go back to the beginning, I believe there is a good chance that invading Iraq will work against isolating the hard core.