How come you always ask me the hard question? Just kidding. Anyhow, I think you will be surprised when I say that I believe Bush messed up when the U.S. first invaded Afghanistan.
Honestly, I do not buy the old argument that Afghanistan is the graveyard of foreign armies, that the British and the Soviets met their matches there and that the U.S. was to be the next in line. For the British, it was clear that the only reason they were interested in Afghanistan was to prevent the unpredictable Tsars of Mother Russia from going south and threatening the British crown jewel, which was India. Once the Tsars got preoccupied elsewhere, notably from the double-threats from both the United Germany and the Japan Empire, the British in essence left the Afghanistan alone.
In case of Russia, the Carter administration seemed to provoke Russian intervention, otherwise the Russians were willing to leave Afghanistan alone. The main reason why the Soviets were bogged down there were the heavy involvement of both the U.S. and Pakistani governments in funding the mujaheddin. Plus, the Soviets under Andropov were not really keen on intervening there. Chernenko intensified the war, though later Gorbachev, seeing how bankrupt the Soviet economy was, decided to pullback.
In Bush's case, he made great decisions in the first months of invasion. He allied the right people and picked the right strategy, leading to the collapse of the Taliban's forces. Then, the White House got preoccupied with the Iraq war.
The Iraq war completely distracted the U.S. administration from Afghanistan. While Karzai seemed to be an adequate choice at the time, the U.S. and the coalition, the ones holding the purse, should have done lots of auditing, making sure that the Afghan central government remained credible and trusted by the population. The inability of the Karzai's administration to stay clean made it harder to gain support from population, especially when things got hairy after the reemergence of the Taliban.
By the time the situation in Iraq stabilized, the Bush administration then faced a very disturbing situation in Afghanistan: the America's lack of attention enabled the Taliban to regroup, threatening the gains that were made in the first several years of the war. Unfortunately, by this point, the U.S. no longer started from a clean sheet, since Washington had a corrupt government in Kabul on its hands The more Karzai and his associates skimmed wealth from Afghanistan, the more credibility the U.S. lost in Afghanistan.
While it is true that the U.S. remained far more respected than the Kabul government (or the al-Maliki government in Baghdad), it created an unhealthy dependency. Basically, the government could make mistakes, pursue stupid policies, since it believed the U.S. would later save the day. At the same time, there is a sense of long-term fatalism among Karzai and his associates: that when eventually the U.S. leaves, the Taliban will likely return and things will look bad, so why not steal enough American aid so they can retire and live in luxury in the Middle East? Such attitudes explain the fact that Karzai and his associates are very keen on make an agreement with the Taliban, as they are not sure how committed the U.S. is to Afghanistan.
Of course, the Obama administration further exacerbated this situation. Indeed, Karzai and his associates believe the U.S. under Obama is far more dangerous than Bush: at least they could rely on Bush, but they are wary of Obama, who came to the White House with the idea of peace, disengagement from both Iraq and Afghanistan, and a retrenchment of the U.S. overseas involvements.
With Obama backtracking on Guantanamo and seeming to pay less attention to Afghanistan, at least early in his presidency, his credibility evaporated in front of Karzai. Karzai then calculated that it would be much better for him to make a deal with the Taliban and Pakistan, making himself the defender of Afghanistan. Thus, he became belligerent, criticizing NATO's bombings, any aerial attacks, etc. He calculated that since the U.S. was leaving anyhow, he had nothing to lose. At the same time, Karzai also relished the fact that the U.S. was not pulling out immediately and would not try to replace him. Therefore, he allowed massive corruption among his supporters and denounced the coalition's accidental attacks on civilians.
So the first part of the blame could be handed to Bush, that his team neglected to ensure that the Afghan government was clean and responsible. The second part of the blame belongs to Obama, because he created a condition of uncertainty, making the Kabul government less interested in destroying the Taliban and far more interested in making agreement with the Taliban and the Pakistanis.
Obama could have done something better. Being seen as a peacenik, Obama could have credibly threatened to withdraw U.S. forces from Afghanistan, should Karzai refuse to make the proper adjustments: that unless he agreed on some reforms, his days were numbered as the US would no longer be there to support him. While it would have been a politically dangerous move for Obama, especially with the Republicans ready to pounce on him, he could have bluffed and Karzai might have offered some compromises, making his government less belligerent. Obama, however, punted. Psychologically, Obama is someone who does not like taking risks. He prefers to get everything in place, understanding everything, before throwing the dice, thus improving the odds.
(Honestly, I think General Stanley A. McChrystal got it right: Obama was not engaged in Afghanistan. Afghanistan was not in his "grand masterplan." For Obama, Afghanistan was a distraction to his precious health care reform. And without the pesky Republicans ready to pounce on him for surrendering the war, Obama would have pulled out the US troops without batting an eyelid.)
What Obama should do at this point is to shore up the government of Afghanistan by demanding, and actually launching, massive investigations on grafts and abuses of power by Karzai's government. This would not endear the U.S. to Karzai, but on the other hand, the people of Afghanistan would love it. Resentment toward the U.S. is growing not solely due to accidental civilian deaths, but for what the population sees as the American support for the corrupt Karzai government.
So what will happen in the future? Assuming that Obama sticks with his schedule, and as long as the central government in Afghanistan remains weak and not trusted due to mass corruption, I believe we will see another civil war on the horizon. Many people, not only the Taliban, despise Karzai, including many governors-cum-warlords who are angry with Karzai's indifference toward their regions. Even though the U.S. might be able to quash the Taliban, forcing them to retreat further to Pakistan, the Kabul government would still have to deal with various regional discontents.
This is a very grim scenario, mind you. Sadly, however, with Obama's lack of interest in Afghanistan, and with the inability of Karzai's government to police itself, to present itself as a credible government of Afghanistan, I really doubt the future of Afghanistan will be bright.