What I personally think he should have said was this:

"Good question Son. Glad you asked. See, the US needs to maintain a military sphere of influence between the resource rich regions of the former Soviet Union and the heavily populated regions of South East Asia. Additionally we would like something of a base between an emerging China and Russia, Pakistan and Iran. You've played "Risk" right? It's a strategic thing see. The terrorism angle is all bullshit. That's just to sell the war to the public. There. Happy now? Great, go pack your bags."