Answer:
Q:What was the stated purpose of the invasion?
A:The purpose of the invasion was the disarm the country of weapon of mass destruction and also to end Saddam Hussein's support for terrorism.
Q:Why did the United States initiate a preemptive war?
A:It was debateble that the threat was not 'imminent' at the time and they were afraid they would send massive destruction.
Q:Were there alternatives to invasion?
A:Yes there was many alternative here's one of them "Allow the weapons inspectors to do their job, which includes sharing intelligence with Hans Blix, pointing out where the smoking guns are being hidden by Saddam, if, in fact there are any."
Q:What was the American public asked to do to support the war effort?
A:Civilians also contributed to the war effort with the purchase of U.S. Government Defense Savings Bonds or "War Bonds."
There's too much you should've posted earlier