The U.S is set to withdraw combat forces from Afghanistan in 2014, and most Americans think that is a good thing. The conventional wisdom holds that whether the Taliban returns to power strictly concerns the Afghans and is of no import to America. The conventional wisdom is wrong. A Taliban-run Afghanistan would be a disaster for America, a sanctuary for anti-American jihadists immune from U.S intervention. If the Afghan government collapses, and the Taliban returns to power, our withdrawal will go down as one of the worst blunders in American history.
Afghanistan is a landlocked country surrounded by nations that would never allow an American army to transit their territory. To the east and south it is bordered by Pakistan, to the west by Iran. This leaves the central Asian Republics and China as the only other access points to the country. China is also unlikely to allow an American army to use its soil to invade another country. The central Asian republics are landlocked and surrounded by Russia and China. Both would be very reluctant to have large numbers of American troops on their soil. This inaccessibility was the reason Mullah Omar did not hand over Bin Laden after the bombing of the U.S embassies, the U.S.S Cole, and the 9/11 terrorist attacks. Were it not for the Northern Alliance controlling the northwest corner of Afghanistan, the Taliban never would have been defeated.
While Mullah Omar may not have much interest in affairs outside of his country, the Taliban owes its success to people who do. Without Pakistan's assistance the Taliban would never have gained control of most of Afghanistan. Pakistan didn't only supply the Taliban with arms and training, it also sent thousands of ground troops to fight alongside them. Further, the Taliban is allied with other elements with strong ties to Al Qaeda, specifically the Hezb-e-Islami and the Haqqani Network. Pakistan has been funding these organizations since the 1980s with the aim of insuring an Islamist and friendly government in Kabul. In practice this means a haven for Jihadist groups waging Pakistan's proxy war against India, including anti-American Jihadists planning attacks on us.
A future Taliban government in complete control of Afghanistan and reliant on Pakistan for aid would be both immune from American interference and a center of world terrorism. Afghanistan may be a poor country thousands of miles away, but it still matters. On its own this fact doesn't justify keeping American troops there, but it has to be taken into account when determining American policy. We can't forget what happened the last time we ignored Afghanistan.