According to Mark Steyn on The Hugh Hewitt Show:
"I think in the months before the invasion of Iraq, the Middle East is a tough nut to crack. But if you're going to find the point at which to try and crack it, Iraq was the one that made sense. And we saw certainly in the early days, the impact it had destroying the Baathist regime, in, for example, Jordan, where at one point, the Baathists were a minor electoral player in Jordanian politics. And in fact, even in a moderate Arab nation like Jordan, the spillover effect from what happened in Iraq, and from the possibilities in Iraq, actually improved the quality of Jordanian democracy. You know, the fact is that a superpower is not a superpower if it cannot influence events in the world. The Middle East exported its pathologies across the planet. That's really what happened on September 11th. And so the only way you can reverse that is by fixing the problem at source, which was the point of going somewhere like Iraq. "
And we should also recall Libya's agreement to dismantle all its WMD's just months after the US swept through Iraq in 2003.