Answer:
so with world war 1 Archduke Ferdinand was assassinated or to be 100% accurate Francisco Fernando de Austria was assassinated, then it caused lots of trouble cos Hitler started blaming it on the Jews, and it started a huge thing between everyone, BUT America didn't wanna join the war, but then Germany sent a note, A.K.A the Zimmerman note, to Mexico stating tht, if they joined the war and helped out Germany, they would help Mexico the land they lost in the Mexican War, but then the British intercepted that note and gave it to us, so then America became angry, and joined the war against Germany
World War 2 on the other hand was with Japan, cos Germany made an attack on Poland, then Japan, Declared War on Germany, and then everyone else joined in, and like all instigators, Japan, Bombed pearl Harbor, and America was like, "Ohmaewa, Mouh Shindeiru" and then Japan was like "NANI???" and here we are