Final answer:
To ensure China's support in American wartime efforts during World War II was the strategic reason for repealing the Exclusion Act, aiming to maintain the critical wartime alliance between the two nations.
Step-by-step explanation:
The strategic reason behind repealing the Exclusion Act was to ensure China's support in American wartime efforts during World War II. The repeal of the Exclusion Act can be seen as a move towards preserving the critical wartime alliance between the United States and China. While there were several other factors at play, including discrimination and economic power dynamics, the core aim was to maintain a strong bond with China, who was an ally against the axis powers and to secure the United States as a power in the Pacific theater.