Making it a state means creating a situation parallel to Quebec in Canada: An unassimilated group of people with a foreign culture, who demand respect for their culture while refusing to join the majority culture.
Giving it independence means it will soon be taken over by someone like Castro or Chavez. Not long after that, the Russians or the Chinese will be invited to move in with their missiles. We don't need a second hostile base just off our shores.
Maintaining the current status is the least bad solution.