If you want to be a cosmopolitan you have to find a cosmopolis to identify with. If you want to be a provincial you have to identify with your province. But it's "provinciality" itself that's important, not the particular region or locality. It's not as though rural North Carolina, rural Ohio or rural Louisiana and rural Oregon are at daggers drawn. Or as thought there is some uniquely Southern or Western essence that distinguishes them from other country people. I don't use "provinciality" in a bad sense either. There's much of value in provincialism.
Probably, the broader point about 9/11 isn't just that a Carolinian might feel something in common with New Yorkers of the outer boroughs. I doubt this is something new for Reed. If it is, I'd worry about him and ignore his article. The broader point is that American provincials and cosmopolitans are finding that they may have things of value in common across the cultural divide. It won't last, but it is something to bear in mind.
In a deep sense, it will always last. What will finally go away is the wonder we discovered when we remembered how much we love each other as Americans. Let's face it, we are all naturally competitive. We break up into sides on just about everything from big things like national politics right on down to small things like inter-school rivalries. It's a part of us.
Whether it's an earthquake in California or a flood in Baton Rouge for a brief moment in time we let down our tough guy stance and rush to the aid of our countrymen. We're like a big Italian family, always fighting and bickering, but GOD HELP anyone from outside who even attempts to hurt "one of us".
Face it, we just love to fight. We're Americans.