I don't disagree with the general gist of your post, but I don't think you fully understand the differences between Iraq and Afghanistan. Terrain has been a problem, just as it was for the Soviets. This isn't like Iraq where much of the fighting takes place in cities or at least decently-populated villages. The Taliban dart in and out of caves in the mountainous regions along the border, and U.S. troops often don't pursue because they don't know the terrain and are sitting ducks if they pursue on foot. Targets are hard to come by, and intelligence gathering is a guessing game.

As for the ethnic differences, it's a bit more complicated than the Shia/Sunni/Kurd breakdown in Iraq. Tribal affiliations and provincial “governments” hold more sway than the central government. Many of the outlying areas are cut off physically and financially from Kabul. Many villages are populated by a mix of former Taliban fighters, former anti-Taliban, former Communists, and general bystanders. Former enemies still hold grudges from the nearly 30 years of fighting, and people often falsely report their personal enemies as Taliban to U.S. forces.

Although the military side is important, it's not going to work unless the country is rebuilt. There aren't even solid roads connecting many of the provinces to Kabul. McCain did mention a lot of these non-military points in his speech, but I think we have to be careful about assuming similarities between Iraq and Afghanistan. Even a counterinsurgency strategy will be limited unless the border region is secured, and that won't happen unless Pakistan gets involved on their side. Dealing with Pakistan, I think, will be the biggest challenge of this whole mess.