This is probably true, as music was present in all cultures, and it is argued that music might have been part of the culture of the human population before it split and populated all the continents.
Answer: To show loyalty to the U.S., gain upward mobility and/or Citizenship
Explanation: During World War II, many Americans of Japanese descent volunteered to join the U.S. military. This was in spite of growing sentiments against them as well as internment of Japanese Americans in camps.
It was a way to show loyalty to the U.S. For some it was the only way to gain citizenship, as well as move up the social ranks as ethnic minority groups had limited rights. They were first rejected, with the exception of bilingual Japanese Americans who helped with translation and interrogation.
The primary way in which these nations built empires was through pure destruction. They would come into these small island nations and simply wipe out populations and take control of the government.