Which of these countries declared war on the United States in WWII?

When war broke out in Europe in September 1939, Thailand declared its neutrality, much to the distress of France and England. Both European nations had colonies surrounding Thailand and hoped Thailand would support the Allied effort and prevent Japanese encroachment on their Pacific territory. But Thailand began moving in the opposite direction, creating a “friendship" with Japan and adding to its school textbooks a futuristic map of Thailand with a “Greater Thailand" encroaching on Chinese territory.