One reason why United states fought in ww1 was because the Germans attacked a U.S Navy boat,Another reason why is because the primary events that led to the United States declaration of waragainst Germany were the Zimmerman Telegram and Germany's announced intention to resume unrestricted submarine warfare. American sentiment had leaned toward the Allies and against the Central powers for some time.
I researched this question and after the Romans were attacked by the Goths (a Germanic people) it went on to explain how the Slavs settled in Ukraine. I apologize if this isn't correct
