The 2003 invasion of Iraq was necessary because at the time the United States though that Saddam Hussein and his government were hiding weapons of mass destruction. In addition, Hussein was a leader who we had been at war with before, and he most likely would have caused destruction to American soldiers again.
The invasion of Iraq was completely unnecessary. It has been proven since that Iraq had no connections to Al Qaeda, nor was it developing weapons of mass destruction. It was of extremely little or no threat to the United States. The invasion diverted needed resources from the War on Terror and ultimately only benefited Islamist extremists.
People after 2001 were very angry in the United States about what had happened with the terrorist attacks on the World Trade Towers and President Bush wanted to look like he was taking aim at enemies. But Iraq was not responsible for the terrorist actions, and this was an awful move.
No, I do not believe that the 2003 invasion of Iraq was necessary. There were talks that there were weapons of mass destruction in the country, but in the end none of these were found. Not to mention the person or group that was supposedly behind the 911 attacks were out of Afghanistan not Iraq.
The 2003 invasion of Iraq was pointless. Not only did it result in the deaths of thousands of American troops, but it also resulted in thousands of innocent Iraqi civilians dying. There were never any weapons of mass destruction. The administration must have known this. The war was an incredibly expensive (in terms of lives lost and money) mistake.