In a confederacy, there is no such thing as a strong central government and the purpose of a confederacy is to protect the states in it from foreign incursion, not to solve domestic problems which are all handled by individual local governments. The articles of confederation established such a confederacy of the first states and they needed the constitution in order to turn into a federation.
It was the "Articles of Confederation" that made the initial US system of government a confederacy, since this provided for a very "weak" central government that left most of the power to the individual states.
