America's wars fall into two important categories.
During wars like World War II, you could ask most Americans about the ideologies of the axis countries and their answers would have been largely accurate. Hitler attacked his neighbors out of the blue, for reasons they did not know. He believed he was part of a master race, etc. Those were facts that even Hitler himself would not have denied.
In Vietnam there was a rationale presented to the American public to justify the war. That rationale was debunked by the "Pentagon Papers". Even so, Americans who wanted to support the war attached on to any bizarre theory that they could. Ultimately, not a single justification for the Vietnam war turned out to be true. Even today there are people who cannot bring themselves to say 58,000 American lives were thrown away so they cling to the remnants of the lies that were more believable decades ago.
More importantly, very few Americans were able to understand the motives of the people we were fighting. The official explanation was that they were part of a vast communist conspiracy. The truth was much more mundane. They were nationalists, with local interests, between two superpowers who were using them as pawns. There was evidence, from the very beginning, that people in the U.S. government had deliberately downplayed their (North Vietnamese) influence, to make a war look more winnable. It is probably not coincidental that the Vietnam war followed on the heels of Eisenhower's "Military Industrial Complex" speech.
In Iraq and Afghanistan, as in Vietnam, the motives of the enemy are kept deliberately mysterious. There are vague hints of "global jihadists" and the average American sees the foe as a wild eyed proto human whose primary goal in life is to kill "infidels". Obviously Iraq and Afghanistan are in a category with Vietnam, and not with WWII.
This is much more important than it appears. It indicates a) an agenda behind the war. The deliberately distant humanity in the foe now goes far beyond dehumanizing a genuine enemy. This is a created enemy, made to serve a purpose. b) a bad outcome. In a war there must be people who understand the enemy with no lies. That type of person is very rare in America, and is not permitted near the battlefield. The war is being sabotaged by those same people promoting it. Ask yourself why that would be.
Long after the War on Terror is over, America will still be reaping its fruit.
Debate over whether the war on terror has made America safer has been leaning more and more toward "no". There are now even key policymakers who are saying the Taliban has grown stronger since the surge.
Even ignoring any overt damage to American security, there is the issue of how the perception of America is being changed by the tactics of the war. There is not one single part of the world where America's image has improved as a result of the war. If you read news sites in the capital cities of our allies you will read endless diatribes about our "imperialism" and how we are dragging them down. America, in 10 years, has gone from the leader of the free world to a bullying monstrosity that foreign politicians must make excuses for.
Depleted uranium was used frequently in Iraq by coalition (i.e., basically U.S.) forces. The use of depleted uranium had some minor advantages to the soldiers, and some significant disadvantages to the local population, including horrific birth defects. It has been used in various conflicts with similar results.
For generations, many people will associate "American security" with creating birth defects in innocent families. Imagine a person who was an Iraqi teen at the time. He or she goes to college and gets a prestigious government job. There will be lots of times when that person has to make a snap judgment for or against an American, or U.S. interests. Again and again they will take a small measure of justice when they can. Multiply that by hundreds of thousands.
Most of the people who the United States has fought, and is fighting, in Iraq and Afghanistan are either tribals or very close to tribal. That basically just means they have little or no formal education and no real concept of national interests or ideologies, beyond what they have learned in their small groups. These are people who are very easily managed. Pakistan has a history of managing that type of people well enough (until they were paid billions of dollars to manage them differently).
America brought the most sophisticated weaponry in the world to a region where ancient rifles are the norm. And still, America has not come close to anything resembling a win. So the next step was to bring a new high tech weapon, drones, into the fight. Drones allow a lot more killing of the tribals with a lot less risk to troops. But is this beneficial to America? Aside from the regular mistakes (i.e. killings of civilians) is it smart to be killing people who could easily be managed and made allies through non military means?
Thousands of people have been killed by U.S. drone strikes, including hundreds of children and other civilians. That includes only known drone strikes. Presumably secret strikes are also lethal.
As with depleted uranium, we have created a vast reservoir of resentment, even hatred, that will last for a generation or longer. Literally millions of people in primitive areas have come to hate the United States for its heavy handed killings of tribal people. Overseas there is significant coverage of American tactics in war. The vast majority of it negative. How does this help America? The people we have killed, and are killing, are almost all simple local people who have never even traveled 20 miles outside their local area, much less ridden a plane or visited another country. A tiny few of them fall outside that description.