Causes

Problems with the Articles of Confederation
The Articles of Confederation were weak and this separated the states. They were not effective in creating a unified national government. The Articles lacked the authority to levy tariffs or deal with imports or manage the economy. People were more loyal to the states than to America as a nation. The federal government had no power. It was hard passing laws in the new nation under the articles. Congress had to have at least 9 of the 13 states to agree before any law could pass. This made it very hard to get anything done. As there was no executive branch, there was no way for Congress to carry out laws they passed. There was no Judicial branch to interpret the law. Other problems faced the young nation as well. Congress did not have the power to collect the taxes needed to pay for the expenses of the national government. With no power to force states to pay the taxes, they could not pay the nation's debt nor provide services.
Under the Articles, the national government could not control trade between the states or with foreign nations. Each state regulated its own trade, which resulted in many disputes among the states and with other nations as well. In addition, most states issued their own money. Without a uniform national currency, trading was a difficult process.
Even though the Articles helped to unify our nation, there were many problems that came with it. The main reason that it failed was because the states did not give the government enough power to run correctly. The national government was too weak to solve problems or carry out laws. One of the key things that determine America's need to change their government was Shay's rebellion. The rebellion revealed that the country was not able to hold domestic order and stability, and they had to change. As a result, in 1787, Congress asked the states to send representatives to a meeting in Philadelphia to discuss what could be done to improve the national government
The American Revolution
After the revolutionary war, the Americans had defeated British rule and were in need of a government for unity. The British left the new infant country completely to itself.While many problems surrounded the country, the American revolution left a beacon of hope to the world. No nation since the ancient Greeks and Romans had attempted to rule on a democratic republic. All nations were looking to America. Whether  or not the new nation succeeded or failed hinged on the fact that America's government worked. Not wanting their great experiment to fail, America tried to govern itself using the Articles of Confederation, and later, the United States constitution.
As soon as countries saw America's revolution pay off, they started to rebel against the Old World governments too. France had their French Revolution, and several  nations in South America fought for independence against  the imperialist nations that owned them.

Effects

The U.S. Constitution set up a federal system that divided power between states and the central government. Separation of powers was practiced, and there were three branches created: the legislative branch, the judicial branch, and the executive branch.
The government had limits but also had power over the states.
The U.S. Constitution  encouraged more citizen participation since it was going to be the first time people actually had a say on who would lead them.
It allowed for the creation of the Bill of Rights because people were worried about the constitution taking their rights away.
The U.S. Constitution gave the federal government more power and allowed them to effectively levy tariffs. Laws were passed and they had to be followed.
The U.S. Constitution influenced the constitutions of many nations.
Its one of the oldest Constitutions in the world.
The Constitution created checks and balances. This made sure no branch or party over powered the other. 
Power was always checked and made sure there was an equal balance to avoid creating a monarchy system.
The Convention was composed of white wealthy males making it hard for the poor to take part.
The U.S. Constitution also can be considered to have contributed to the French Revolution in 1789. The model of the constitution inspired the constitution of France.
The U.S. Constitution also effect the Far East, especially in Southeast Asia. Many of the countries became democracies and modeled their constitution after the U.S. Constitution. Malaysia, adopted the concept of separation of powers from the U.S. Constitution.