If we leave Afghanistan, the Taliban will take over, Al Qaeda will re-establish itself there, and new and deadly attacks on America will be more likely.
The Taliban are unpopular in much of Afghanistan and unlikely to take over the country. They might regain power in some areas, but Al Qaeda cannot recreate its former haven because—unlike before 9/11—the United States can easily detect and destroy bases and training sites with air power or special forces. Further, our large-scale military presence there may actually be increasing the overall danger that we face back home. Anger at U.S. military action in Central Asia inspired Faisal Shahzad, a U.S. citizen, to attempt an unsuccessful car bomb attack in Times Square. Other home-grown terrorists appear to have been inspired by similar motivations.