When a former Afghanistan interior minister compares the two by saying "Afghanistan is not Iraq", he is implying that Iraq was a cakewalk by comparison.
I am no military expert, but I doubt it in principle. It seems that had the Bushies not been in such a hurry to engage Iraq, the campaign for Afghanistan would have turned out better. And of course, if Charlie Wilson's version of events (a v ery interesting movie except for the as-always insufferable Julia Roberts, by the way) holds any water, even that should never have been necessary; blame for that falls to both parties and typical congressional shortsightedness.
In practice, though, the volunteer military is tapped out and so is the world's tolerance for American military adventures. This needs to be a NATO campaign or it will be NOT A campaign.