Why previous overseas nurses dont count their experiences once they hired in a hospital? Only US experienced were counted.

The nursing training and experience can vary differently from country to country as well as the type of hospital that the nurse worked in. What may be done in one country is not necessarily done in another. The international nurse is going to have to prove that he or she is safe, is able to read and speak English well as well as prove that their skills are safe, competent, and up to date.