I think perhaps Obama knows that the US has 50 states.
Whereas it didn't appear that Romney gaffed. He was just making it up as he was going along and turned out he had no idea what he was talking about.
So I think your desire to escape addressing Romney's failings by making a weak comparison to Obama doesn't work too well for me.
Saying 57 states doesn't speak to vacuity. It speaks of tiredness. Winging it on the reason for Syria's relationship with Iran is a mistake of a different kind. He clearly has no idea why Syria and Iran are allied.
Not sure Romney is dumb. But on foreign policy, I thought he was vacuous. And for debate purposes, he pretended to believe things other than he has been stating on the trail. So he insulted the people whom he wishes to vote for him by not exposing his ideas to daylight.
For myself, I think he will be a neocon. And that the pose he struck for the cameras was fiction. More torture is on the menu. More wars of choice. More waste of treasure. He pretended to be Obama. But he's just another neocon puppet.