The 1st "World War" was just an exaggerating term, in fact most countries participated in the War were European nations. Just because Japan, United States and China "joined" in to make it "World War".
The 2nd World War was truly in global scale, most countries around the World took side and participated. Originally there were two separated war, that was European war between Ally and Germany, and War between China and Japan. Only after Pearl Harbour Attack when United States joined Allies formally to make the War really global. Although we often count 1 September 1939 as start of WWII, this was only start of European War. The war really became global since 1942 when Allies began to counter strike back Axis Powers.