Here's an interesting post on the Molten Thought blog about what Vietnam--and the rest of our surrenders since--have done to the perception of America in the world. He's quoting Mark Steyn, and here's the money quote:
But if you lived in Damascus and Moscow and Havana, the Vietnam war was about America: American credibility, American purpose, American will. For our enemies today, it still is. Osama bin Laden made a bet – that, notwithstanding the T-shirt slogan, "These Colors Do Run": They ran from Vietnam, and they ran from the helicopters in the desert, and from Lebanon and Somalia – and they will run from Iraq and Afghanistan, because that is the nature of a soft, plump ersatz-superpower that coils up in the fetal position if you prick its toe. Even Republicans like Sen. John Warner seem peculiarly anxious to confirm the bin Laden characterization.
It's been said, and I believe it's true: our Islamic fundamentalist enemies only understand strength. Show them weakness, and it emboldens them. Show them strength, and they'll wilt like the cowardly fanatics they really are.