Final answer:
The Articles of Confederation featured a weak central government and unicameral legislature with no judicial branch, while the U.S. Constitution introduced a strong central government with a bicameral legislature and separate judicial branch.
Step-by-step explanation:
The transition from the Articles of Confederation to the U.S. Constitution marked a significant shift from a confederation to a federation political system in American history. Under the Articles of Confederation, there was a weak central government with limited executive powers, a unicameral legislature, and no judicial branch. However, political, social, and economic challenges demonstrated the need for a stronger federal structure. Consequently, the U.S. Constitution established a strong central government, a bicameral legislature under a federal system, and a separate judicial branch. These changes provided the framework for a more effective national governance, balancing the powers between the nation and the states.