simplify
This is a war against Islamo-Fascist Terrorist with the International Front being Iraq. The IFT's made that decision. It is best we keep them busy over there lest they get busy over here.
Obviously you're not familar with the terms of the cease fire that brought an end to the actions in the Gulf War. In addition ending hostilities toward his neighbors, Saddam was to discontinue all WMD Programs and allow UN inspectors to verify that he had actually done so. Instead, he defied the UN and the international community by expelling the UN inspectors. In doing so he violated the terms of the cease fire agreement. When an agreement between two or more parties is breached it no longer exists and the violator enjoys no rights or protections as when the agreement remained in effect. It was understood by all parties concerned that any breach of the Cease Fire Agreement would or could cause the hostilities to resume. Saddam was given 17 'second chances' to comply with UN resolutions yet he remained defiant.
Maybe the invasion of Iraq was not necessary in that no WMD's of any significance was ever found, but, Saddam was menace to his neighbors, a murderer of his own citizens and a possible threat to the world in general. By not really knowing whether or not he had WMD's and knowing that if he did he would probably use them again as he had done before, he could not be trusted. While he was never connected to the atrocities of September 11, 2001 he was by no means above the use of terrorism. Our leaders, both the President and the Congress could not allow any Weapons of Mass Destruction that he may have had and they all thought he had to fall into the hands of those who we know want to do us harm. For that reason, the President suggested and the Congress of the United States of America agreed that Saddam should be dealt with in such a manner as set forth in the original Cease Fire Agreement.
Just because the war in Iraq is not going well is no reason to 'tuck tail and run'. That's un-American. War is never a good thing but it is sometimes necessary. This is one of those times.