As I noted earlier, I think the process will take far longer. It does not help that Afghanistan is currently ranked the 2nd most corrupt government in the world, trailing only Somalia. Without a credible government, the US could send 100,000 more troops and still fail in Afghanistan. COIN folks from Gen. McChrystal to David Kilcullen have said that more troops will help, but there's no guarantee that they can bring victory.
Senator McCain may be relying on memory of the Iraq surge, and its success. Several factors make that a faulty comparison.
- As flawed as the Iraqi government was, it still had a far more organized and effective military and police force.
- The "Accidental Guerrilla" phenomenon that Kilcullen wrote about was actually backfiring in Iraq. The "Sunni Awakening" and backlash against AQI*, as well as Muqtada al-Sadr's decision to ask his militia to at least temporarily stand down were both almost the opposite of what is happening in Afghanistan.
- Contentious parts of Iraq like Baghdad had been almost entirely ethnically cleansed by the time the surge took effect. Sunnis and Shi'ites were no longer living in the same areas, and violence went down as a result.
- Iraq had neighbors that, not to put too fine a point on it, were not Pakistan. It is news to nobody that insurgents cross between Afghanistan and Pakistan at will. This makes it incredibly hard to defeat the insurgency in Afghanistan.
- Iraq and Afghanistan are very different places, culturally. Iraq, for all the faults of the Hussein regime, was a secular and modern state in the Middle East. Afghanistan is far less modern, far more tribal, and certainly not as secular (a Taliban government saw to that).
*Al Qaeda in Iraq