Final answer:
The Marshall Plan supported the broader U.S. policy goal of containing communism by rebuilding European economies after World War II, thus bolstering democratic governments capable of resisting Soviet influence and creating markets for U.S. goods.
Step-by-step explanation:
The broad U.S. policy goal of the mid-twentieth century that was supported by the implementation of the policy proposed in George C. Marshall's speech was the containment of communism and the promotion of economic stability in Europe as a means of bolstering democratic governments and resisting Soviet influence. This policy was operationalized through the European Recovery Program, commonly known as the Marshall Plan.
The plan involved providing over $12 billion in economic aid (equivalent to around $147 billion today) to European nations to rebuild their economies, which in turn would create stable democracies capable of resisting communist threats and reopening markets for U.S. goods. By restoring the economies of Western Europe and preventing the spread of communism, the United States aimed to maintain political stability and peace in the region while also benefiting from a revitalized European market for American products.