They do not act in concert in their economic affairs. National trade statistics are nothing more than arbitrary aggregations of many separate acts of exchange. I don't either. If it makes sense to worry about the deficit between the United States and Japan, then maybe we should worry about the deficits among the states. Maybe Philadelphia has an intolerable deficit with Toledo that we're not being told about it.
Neighborhoods can have deficits too.
Come to think of it, I have a huge deficit with the corporation that owns my favorite supermarket. I spend a couple hundred dollars a month there, but that corporation buys nothing from me. On the other hand, I rarely purchase things from the people who do buy from me. The fact is, if the balance of trade doesn't matter at the personal, neighborhood, or city level, it doesn't matter at the national level. Adam Smith was right.