Final answer:
Germany was viewed as the aggressor by the US due to their violation of the Treaty of Versailles, which included rebuilding a military and occupying the Rhineland.
Step-by-step explanation:
One of the reasons the United States viewed Germany as the aggressor during the lead-up to World War II was Germany's violation of the Treaty of Versailles. This treaty, which ended World War I, aimed to limit Germany's military capabilities.
However, under the leadership of Adolf Hitler, Germany began a covert military buildup, introducing compulsory military service and ultimately occupying the demilitarized zone of the Rhineland, near France's border. Despite these aggressive actions, Western democracies initially opted for a policy of appeasement, hoping to avoid another devastating conflict.