They aren't. They do represent more of the population and land area. Also many cities, probably most, are awful. Memphis, TN or Dayton, OH are much more representative of the nation then New York or San Francisco.
> Why should the rest of us be heavily taxed and regulated just to preserve these anachronistic, unproductive communities?
That really hasn't been a question in this discussion. The international order is built on nation-states. Whether you like it or not, the nation implies collective responsibility. This was the "fraternité" part of the French revolution, for example. Your remarks reflect the prevailing liberal sentiments that we are all just individuals. If we are these atomic subjects, why should we be obligated to help some random other atoms? This is one of the reasons why liberal democracies are failing. The left and establishment have no good response to this. The alt-right has pushed people to revive ethnic (Richard Spencer) or civic (Steve Bannon) nationalism.