What international relations theory can best explain the second us-iraqi war

For my IR 6652 research proposal, I plan to discuss what international relations theories can best explained the US reactions to the 9/11 attacks. In specific I plan to discuss the road war of justification that US utilized to justify war against Iraq. I plan to answer the following questions:
What theory best explains US reaction?
What other theories can also explain the situation?
What are the similarities and differences between theories?
Are there any other similarities in history?
Are there any lessons