Remember that when you attack the Iranian government (which I assume is what you want to attack) you have to do it in such a way that it doesn't undermine the Iranian opposition. The fundies were on the defensive in 2003 before the Iraq invasion, but that cut their feet from under the reformers, allowing the religious nutcases to rivet their control in place for another few years.

It couldn't possibly be that the religious nutcases in the West would prefer an Iran run by other religious nutcases to a secular, prosperous, liberal Iran, could it?