The cause of the American constitution was the failure of the previous system of government, the Articles of Confederation. The Articles governed the colonies during the stress of the American Revolution, but after the war was over, the states started to diverge. The main issue under the Articles was taxation--the federal government could not pass a tax to pay for the debts incurred during the war. Some states did not want to pay for the debts of other states--it was similar to friends fighting over a shared check after eating at a restaurant. There was also the issue of how to fairly dispense the land gained from the war with Britain--several states had conflicting land claims that stretched to the Mississippi River. What brought the issue to a head was when farmers in western Massachusetts who had fought in the Revolutionary War but were not paid for their service started to lose their farms due to their inability to pay property taxes. In what would be known as Shay's Rebellion, the Founding fathers realized that a federal government was needed to take over the fiscal duties of the new government.
The effects of the Constitution produced a government with three equal branches--legislative, executive, and judicial. The Articles were only considered a legislative body. It placed federal law above state law, but left some powers to the states under the Tenth Amendment. In order to please those who worried about a tyrannical national government, the Founders also included a Bill of Rights in order to safeguard what they considered to be essential liberties. The Constitution set up a bicameral legislature but made sure that taxation bills always began in the House of Representatives which has always been elected by the people by districts. The Constitution continues to be the governing document of the United States and while it has been debated and interpreted differently over the years, it continues to grow and be amended to serve the nation's needs without a radical overhaul.