The reason given for invading Iraq was that Saddam had WMD's in violation of the treaty. The White House also told the Senate that some were capable of hitting the east coast of the US.
Now, the UN inspectors continued to say that over 95% of Saddam's WMD's were already disposed of based on the serial numbers from the US, British, and French companies that sold the stuff to Iraq. What little he had left was either buried, or some of it most likely did get smuggled out. But he had very little according to the US military when they finished there search for WMD's.
Also the White House claimed to have proof that Al-Qaida was working with Saddam. There has been no evidence of this.
Also the White House fostered the perception that Iraq was partly responsible/involved with 9/11. Thanks to faux news for pushing this piece of White House propaganda.
Add in the fact that Shrub was itching to go in and finish what his daddy started means that all this administration needed was the flimsiest of exscuses to go into a country that they have always wanted to invade.
There has been accurate reports by people stating that the White House has been obsessed with Iraq from the first day they took office.
To many of the US's resources are being sucked up by Iraq instead of being used to go after Osama who should be our number 1 priority.