That is precisely...
...the point the terrorists behind these attacks were trying to make...that it doesn't matter that we've toppled Saddam, that they can and will continue to conduct acts of terror against western interests in the Middle East.
These attacks were well planned and orchestrated by an organization that had little connection to and no reliance upon the former Iraqi regime.
But lets face it...they would have eventually acted whether we invaded Iraq or not. The motives behind these acts are driven by an irrational religious fervor to drive us from the region.