Final answer:
The military objective valued the most by Britain and the USA was the defeat of Germany in World War II.
Step-by-step explanation:
The military objective that Britain and the USA valued the most when discussing US entering the war was the defeat of Germany. The United States had a gigantic industrial capacity and millions of fresh troops that could be called up, while Germany's supplies were running thin after nearly three years of total commitment to the war. In addition, Roosevelt leaned towards a 'Europe First' strategy, focusing on achieving victory over Germany before turning attention to Japan. This objective was driven by the belief that defeating Germany would secure freedom and establish the United States as the preeminent world power.