Who didn't join world war 2?

Most of the countries in Africa, some South American countries and a few Central American Countries. It is easier to show you who joined the war effort than to show you who did not join either the Allied Forces or the Axis Forces.

Allied Nations

Ethiopia · China · Czechoslovakia · Poland · United Kingdom · India · France ·Australia · New Zealand · South Africa ·Canada · Norway · Belgium · Netherlands · Greece · Yugoslavia · Soviet Union ·United States · Philippines · Mexico ·Brazil

Axis and

Axis Aligned

Nations

Bulgaria · Reorganized National Government of China · Croatia · Finland · Germany · Hungary · Iraq · Italy · Italian Social Republic · Japan · Manchukuo · Romania ·Slovakia · Thailand · Vichy France

Underground Resistance

Nations

Austria · Baltic States · Belgium · Czech lands · Denmark · Estonia · Ethiopia ·France · Germany · Greece · Hong Kong ·India · Italy · Jewish · Korea · Latvia · Luxembourg · Netherlands · Norway ·Philippines · Poland (Anticommunist) · Romania · Thailand · Soviet Union · Slovakia ·Western Ukraine · Vietnam · Yugoslavia

Neutral Nations: Switzerland, Portugal, Spain, Ireland and Norway.