I'm sure some "anti-war elements" would be screaming, in the same way that some on the isolationist Right are always screaming. That does not translate into real political opposition.

Polls taken in late 2001 showed 90% support among Democrats for the war in Afghanistan, vs never much above 50% even during the spring of 2003 in IRaq. Afghanistan. Afghanistan hasn't been polled much recently, but a January 2006 poll showed that 70% of the public thought it was right to have gotten involved in Afghanistan, vs 20% saying it was a mistake (compared to 50-50 on Iraq at the time).

These numbers are without much of an Administration sales job on Afghanistan, and with spillover unhappiness from Iraq. If we were only involved in Afghanistan, and the case were frequently being made that we were fighting the very forces who attacked us on 9/11 or at least who harbored those attackers, I'm quite confident the administration would be able to maintain adequate support for a more robust effort. Go try to find a groundswell of support for pulling out of Afghanistan on DailyKos or other liberal discussion forums -- it's not there.

Now I'm sure there'd be a Cindy Sheehan and ANSWER out there and if that gives you indigestion, sorry, but you sure wouldn't see 35% presidential approval ratings and the loss of Congress over it. People do look at Afghanistan and Iraq differently.