The Baltic states of Estonia, Latvia, and Lithuania, jointly declared their neutrality on 18 November 1938, in Riga, at the Conference of Baltic Foreign Ministers with their respective parliaments passing neutrality laws later that year. Despite that, all of them were occupied twice by the Soviet Union and once by Nazi Germany.

Spain, whose civil war had just ended at the beginning of World War II, sent troops to the Russian front to help German armed forces. I don’t think they ever declared war.

Nazis purchased critical war material from neutral countries using Swiss francs gained in exchange for gold looted by the Nazis from occupied countries and from individual victims of concentration camps. Switzerland continued to trade until the end of the war in 1945.

The Phillipines was attacked 9 hours after Pearl Harbor on 12/7 and did not declare war but was drawn into it as a result of the attack. The US declared war on 12/8 and had war declared back on 12/11.