Final answer:
James Monroe was the sole president to agree on the Monroe Doctrine during its creation in 1823, with John Quincy Adams as the principal architect. While the doctrine stated strong U.S. opposition to European colonization in the Americas, enforcing it would have proven difficult without European acquiescence.
Step-by-step explanation:
Only one president, James Monroe, agreed on the Monroe Doctrine at the time of its issuance in 1823. Secretary of State John Quincy Adams played a significant role in crafting the doctrine, though Monroe ultimately gave the final approval and announced it in his annual message to Congress.
The Monroe Doctrine was a cornerstone policy asserting that any attempts by European powers to colonize land or interfere with states in North or South America would be viewed as acts of aggression requiring U.S. intervention. It underscored the difference between the political systems of the Americas and Europe, promoting the concept of separate spheres of influence for the two continents.
This doctrine symbolized the United States' growing sense of diplomatic independence and set a precedent for future U.S foreign policy, although many were unaware that enforcement would have been challenging had European powers decided to challenge it.