Michael Lind has a vigorous critique of cosmopolitanism. Extract:
Contemporary cosmopolitanism, in defiance of Hume, combines an “ought” with an “is.” The “ought” is the view that the nation-state is a parochial form of organization and should be replaced by broader, more inclusive loyalties. The “is” takes the form of the claim that the nation-state is destined to wither away because of irresistible technological or economic forces, whether we like it or not.
… Fortunately, most of the world-order goals of cosmopolitanism can be achieved by enlightened liberal internationalism without the need to sacrifice or weaken the democratic nation-state, the organization in which most of the progress toward equality and economic security over the last three centuries has taken place.
That is one of the most concise descriptions of cosmopolitanism, and most concise cases for the nation-state, that I have seen.