Believe it or not, a "hung jury" is incredibly rare in the U.S. criminal justice system. If there is a jurisdiction where they are common, that is typically the fault of the prosecutor's office. An effective, efficient prosecutor's office won't file charges unless it is reasonably certain the accused is guilty. Even then, most cases are settled and those that go to court tend to result in convictions. In more disorganized offices, prosecutors tend to file charges in hopes of forcing a plea bargain. The result in those jurisdictions is lower conviction rates, more hung juries and a lot of wasted time.