Nursing education and NCLEX is the minimum standard as outlined by the BON. True, some nursing programs
offer added "extras", but for the most part, only prepare the individual for NCLEX with minimal preparation. There must be some type of standardized training or we'd be all over the place with post-education licensure and as Tweety pointed out, a nightmare.
Once, there were individual state board exams that everyone had to pass in order to become licensed. This was replaced by a national standardized NCLEX. Now, across the nation, the nurse passes the exact same standardized test according to their education.
After the individual is trained and licensed, on-the-job training is necessary to "specialize" in any given area. This may take years to become proficient enough to be considered so and often takes years to be considered an "expert".
The individual may obtain certification in their specialty area to prove added knowledge/expertise in any given specialty. MANY from which to choose.
The title 'nurse' is that the individual met the educative requirements and holds a license from their state BON. It's a legally protected title. Teacher is not and the word, 'teacher' can be used by anyone.