ORIGINAL: Shannon V. OKeets
Thanks.
Then the task is to provide an historical entry date into the war for each of these countries.
I'll bite. Info obtained from Wikipedia only:
Argentina - 27 March 1945 (DOW on Axis)
Australia - 3 September 1939 (DOW on Germany)
Belgium - 10 May 1940 (German DOW on Belgium)
Bolivia - 7 April 1943 (DOW on germany)
Brazil - 22 August 1942 (DOW on Germany & Itlay)
British Guyana Commonwealth - Remained colony of Great Britain until 1966
British Honduras Commonwealth - 8 December 1941 (DoW on Japan), 13 December 1941 (DOW on Germany)
Bulgaria - 13 December 1941 (official DOW on UK & US)
Burma Commonwealth - Remained colony of Great Britain until 1948
Canada - 10 September 1939 (DOW on Germany)
Chile - 1945 (DOW on Japan)
China - 7 July 1937 (Marco polo bridge incident, leading to IJA invasion by end of month)
Colombia - 26 November 1943 ("Status of Belligerency" on Germany)
Costa Rica - 8 December 1941 (DOW on Japan, with DOW on Germany & Italy a "few days later")
Cuba - 8 December 1941 (DOW on Japan), 11 December 1941 (DOW on Germany & Italy)
Dominican Republic - December 1941 (DOW on Axis)
Dutch Guyana Netherlands - Remained Colony of Netherlands until 1954 (limited self gov), fully independent 1975.
Ecuador - 1 February, 1945 (DOW on Germany)
El Salvador - 8 December 1941 (DOW on Japan), 12 December 1941 (DOW on Germany)
Finland - eh... Winter War vs USSR (USSR attacks Nov 1939), Continuation War 25 June 1941 (DOW on USSR), Allied member 15 Sep 1944
France - 3 September 1939
French Guyana - Colony of France
French Indo-China France - Colony of France, gained independence 1954
Greece - 28 October 1940 (Italian DOW on Greece)
Guatemala - 9 December 1941 (DOW on Japan), 12 December 1941 (DOW on Germany & Itlay)
Haiti - 8 December 1941 (DOW on Japan, with DOW on Germany & Italy a "few days later")
Honduras - 8 December 1941 (DOW on Japan), 13 December 1941 (DOW on Germany & Italy)
Hungary - June 1941 (DOW on USSR)
India - Colony of Great Britain, gained independence in 1947
Iraq - Officialy nuetral until DOW on the axis in 1942, although occupied by Allied troops in 1941.
Ireland - Although officially a member of the Commonwealth, Ireleand remained Nuetral.
Italy - 10 June 1940 (DOW on France & UK)
Japan - 7 July 1937 (limited war w/China), 7 December 1941 (DOW on US & UK)
Korea Japan - Colony of Japan until 1945 (surrender of Japan)
Malaya Commonwealth - Colony of Great Britain until 1946
Manchuria Japan - Effectively a colony of Japan until 1945. (Head of army was also the Japanese ambassador.)
Mexico - 22 May 1942 (DOW on Axis)
Netherlands East Indies Netherlands - Colony of Netherlands until gaining independence in 1949
Netherlands - 10 May 1940 (German DOW on Netherlands)
Nicaragua - 8 December 1941 (DOW on Japan), 11 December 1941 (DOW on Germany)
Norway - 9 April 1949 (German DOW on Norway)
Panama - (Non canal zone) No mention of involvment in WW2 in Wikipedia.
Paraguay - 8 February, 1945 (DOW on Germany)
Persia - (Iran) Occupied by UK & USSR troops in August of 1941, DOW on Germany in September of 1943.
Peru - 12 February, 1945 (DOW on Germany)
Philippines United States - effectively a colony of the US until 1946
Poland - 1 September 1939 (German DOW on Poland)
Rumania - 22 June 1941 (DOW on USSR)
Saudi Arabia - 28 February 1945 (DOW on Germany & Japan)
Siam - 25 January 1942 (DOW on US & UK)
Siberia USSR - Part of USSR home country
South Africa - 6 September 1939 (DOW on Germany)
Spain - Remained officially Neutral
Sweden - Remained officially Neutral
Turkey - 25 February, 1945 (DOW on Germnay)
Ukraine USSR - Part of the USSR home country
United Kingdom - 3 September 1939 (DOW on Germany)
Uruguay - 15 February 1945 (DOW on Germany)
United States - 7 December 1941 (Japanese DOW on US), 11 December 1941 (German & Italian DOW on US)
USSR - Polish Partition (17 September 1939), Winter War (Vs. Finland Nov 1939), Occupies Baltic States (Aug 1940), 22 June 1941 (German DOW on USSR), 8 August 1945 (DOW on Japan)
Venezuela - 1945 (DOW on Axis)
Yugoslavia - 6 April 1941 (German & Italian DOW on Yugoslavia)
I apologise for any mistakes that may be found here.