What was Japan's primary motivation to wage war on the Western powers, primarily the United States?

Japan declared war against the U. S. in 8 december 1941. That was because firstly, the Japanese had expansionist plans for Asia; secondly, it needed to get back its access to oil and steel; thirdly, it was looking for regions that produced oil, tin and rubber.

Both the U. S. and Japan had expansionist plans for Asia. Things got tenser when the Japanese invaded French Indochina in September of 1940. The U. S. and the British answered with a trade embargo: Japan had become deprived of oil and steel.

Also, the American marine was a barrier to Japanese expansion on the Pacific. Thus the Japanese decided to attack the U. S. and get access to regions that produced oil, tin, and rubber.

This scenario led to the Pearl Harbor attack which changed the power balance in the Second World War (1939-1945) once the U. S. declared war against Axis Powers.