A Federal system of government

Unlike most countries, American has a federal system of government.  Define federalism.  What are the two alternatives to federalism?  Explain each and give examples for all three types of power distribution.  Then, explain the changes or stages in the practice of American federalism from the Articles of Confederation until today.  Finally, compare and contrast the strengths of federalism to the more common approach used by most countries.  Would the US be better as a unitary system or confederation?  Use the history of federalism and explain why or why not.