Final answer:
Certain powers were denied to states in the U.S. Constitution to preserve national unity and prevent states from acting like sovereign countries, which could undermine the national government's authority. This was accomplished through Article I, Section 10, and the Tenth Amendment, balancing national interests with state rights.
Step-by-step explanation:
To prevent conflicts and ensure a unified national policy, particularly in areas like foreign diplomacy and monetary systems, certain powers were expressly denied to the state governments by the Constitution. The Founding Fathers restricted states from making alliances or entering treaties because such actions could undermine the authority of the national government and threaten the unity and security of the newly formed nation.
Article I, Section 10 of the Constitution was designed to prevent states from acting as independent countries, which had been an issue under the Articles of Confederation. Moreover, the ratification debate highlighted concerns about a centralized power, with figures like Patrick Henry advocating for the retention of powers by the states, which led to the inclusion of the Tenth Amendment.
Their intention was to balance the need for a strong national government, capable of defense and unified regulation, with the protection of state sovereignty and the reserved powers of the states. By denying states the ability to make treaties, coin money, tax imports and exports from other states, maintain their own armies, and engage in war, the Constitution aimed to create a system where the national interests prevailed over parochial state interests, while still protecting the fundamental principle of state rights.