Final answer:
The Monroe Administration's foreign policy successes were mainly due to John Quincy Adams's role as secretary of state, promoting trade, expansion, and influencing the Monroe Doctrine.
Step-by-step explanation:
The foreign policy successes of the Monroe Administration were largely the result of John Quincy Adams as secretary of state. Adams was instrumental in shaping the administration's foreign policy, including promoting foreign trade, pursuing continental expansion, and reducing European influence in Latin America. His vision of diplomatic nationalism aligned with President Monroe’s goals, and together they played significant roles in the design and adoption of the Monroe Doctrine, which furthered their objectives and cemented their administration's legacy in foreign policy.