Some Americans do, some don't, it appears that a lot do though.
Really though it was a combined effort by
After the German invasion of Poland:
Poland: 1 September 1939
Australia: 3 September 1939
France: 3 September 1939
New Zealand: 3 September 1939
United Kingdom: 3 September 1939
India: 3 September 1939
South Africa: 6 September 1939
Canada: 10 September 1939
Denmark: 9 April 1940
Norway: 9 April 1940
After the Phoney War:
Belgium: 10 May 1940
Luxembourg: 10 May 1940
Netherlands: 10 May 1940
Greece: 28 October 1940
Yugoslavia: 6 April 1941
After the invasion of the USSR:
Soviet Union: 22 June 1941 (cooperated with Axis during Invasion of Poland)
Ukraine: 22 June 1941
Byelorussian SSR: 22 June 1941
After the attack on Pearl Harbor:
Panama: 7 December 1941
Costa Rica: 8 December 1941
Dominican Republic: 8 December 1941
El Salvador: 8 December 1941
Haiti: 8 December 1941
Honduras: 8 December 1941
Nicaragua: 8 December 1941
United States of America: 8 December 1941
China: 9 December 1941
Guatemala: 9 December 1941
Cuba: 9 December 1941
Philippine Commonwealth: 9 December 1941
Czechoslovakia: 16 December 1941
After the Declaration by United Nations:
Mexico: 22 May 1942
Brazil: 22 August 1942
Ethiopia: 14 December 1942
Iraq: 17 January 1943
Bolivia: 7 April 1943
Colombia: 26 July 1943
Iran: 9 September 1943
Liberia: 27 January 1944
Peru: 12 February 1944
After D-Day:
Ecuador: 2 February 1945
Paraguay: 7 February 1945
Uruguay: 15 February 1945
Venezuela: 15 February 1945
Turkey: 23 February 1945
Egypt: 24 February 1945
Lebanon: 27 February 1945
Syria: 27 February 1945
Saudi Arabia: 1 March 1945
Argentina: 27 March 1945
Chile: 11 April 1945