The answer is more to what degree were nations involved. There were the nations that were fully involved in the Axis (Germany, Italy, Japan) or the Allies (Britian, Canada, USA, Australia, New Zealand), and the occupied countries (France, Belgium, Holland, Norway, Morocco, Egypt, Burma, China, Philippines), and even neutral countries who were involved, (Sweden, Switzerland) because they acted as intermediaries for banking and humanitarian needs. Countries allied or historically tied to nations at war were also involved through association and support of voluntary troops and goods (India, Bermuda, Barbados, French Antilles, Guyana). It might be easier to ask what part of the world was not involved in WW2. A couple of South American countries and some African nations escaped involvement of any kind... that's about it.