James Madison is credited with writing much of the US Constitution. While this maybe an over exaggeration he is credited with many of the rights spelled out in our Bill of Rights. Many of the Bill of Rights came from the Virginia Declaration of Rights. Something that was not envisioned when the Constitution was written was the development of political parties. It didn't take long after our current form of government to exist before two political parties were created with the northern states leaning toward the Federalist party and the southern states leaning toward the Republican party. Interestingly that Republican party of Jefferson and Madison is the party that became today's Democrat party. The Federalist were supporters of a strong central government and the Republican party was a supporter of states rights.
The weaknesses of the Articles of Federation were many. It had no taxing authority, no executive or judicial branch and states rights trumped federal authority. It was a loose federation mostly for common defense although most states had their own militia. It became apparent that a "federation" could not create a unified country that was necessary to address common needs among the states. This reality caused the states to come together to create a central government under our current Constitution.
The current situation in Europe with the European Union reminds me of our country under the Articles of Federation. Individual countries of the European Union still have control over their economies and governance. They share a common currency but not much else. The current debt crisis in some of the countries of the Union show that without the countries of the Union giving up some of their sovereignty the Union doesn't stand much chance of surviving. Just as the states in our early history had to create a central government to exist as a unified country so will the European countries have to create a unified government which has power over the individual countries. An "United States of Europe" with a common governance will come about at some point. The world economy and global communication are moving political governance around the world toward larger unions of countries.