Iraq had nothing to do with 9/11 and we invaded because the Bush bunch claimed, contrary to the evidence, that Saddam had WMD and a connection to 9/11.
In the first video bin Laden released after 9/11 he states the deaths of a million Iraqi's due to the US/British imposed UN sanctions and occupation of Palestine as crimes of the US. In a later tape, censored in the US, he states he got the idea to attack the Tower as far back as 1982 with Israelis invasion of Lebanon and it's siege and destruction of Beirut. When he saw the buildings burning he said he pictured the WTC burning.
He has also stated they want to drive the West from the Mideast which has dominated and controlled the regio, for the oil, since WW1.
The majority of the US troops are lied too as to the reasons they are there but when they get there polls show the majority feel they should leave. Generals and former Generals have also stated we should withdraw as has the Baker/Hamilton report.