Your premise (or your teacher's premise) is flawed. The purpose of the Iraq War was to uphold the ceasefire agreement from the Gulf War in 1991. It is one of the few times in the last half of the 20th century where America actually did what it said it was going to do. And because of that point alone, respect for America increased throughout the world. Today, President George W. Bush garners more respect amongst the Iranian people than he does in this country.
I would recommend that your teacher actually take the time to read the Authorization for Use of Force in Iraq. Then perhaps he/she could offer an assignment based upon something other than ignorance.