Although few Americans seem to have noticed, China and the United States are currently on a collision course -- one that could easily lead to war.  Their dispute, which has reached the level of military confrontation, is over control of the South China Sea, a vast, island-studded region containing a major maritime trade route and rich in oil, natural gas, and lucrative fishing areas.  Both nations would be well-served by backing away from their dangerous military buildups and leaving the job of sorting out the issues to the United Nations.