The visit to Iraq by Iranian president Mahmoud Ahmadinejad highlights yet another bit of blowback from the Iraq war. I did a piece before the war that sketched Mesopotamian history and explained the ethnic/religious landscape, noting that the majority Shia had an affinity for and connections with Iran. Shortly thereafter any number of commentators noted that one impact of removing Saddam Hussein, Iran's mortal enemy, from power, was to increase the regional power and influence of Iran.
I don't think it's helpful to analysis to label certain regimes as "devil states." Every government has more than a bit of the devil in it. The Iranian regime is much more complicated than simply being an anti-American machine. But if one is concerned about Iran's growing regional influence, as is not unseemly, one would have hoped somebody among the geniuses touting war with Iraq in 2002 would have considered the likely impact of enhancing Iran's influence and power.