The United States is a federal government because of the philosophy of its founding fathers. The founding fathers realized that a country needs a strong federal government in order to function properly, but they also realized that there needed to be limits on its power. A federal government includes checks and balances to guard against governmental misconduct.
The United States is considered a federal government because it is run by a group of officials that the people elect. The origins of the federal government started in the United States with the first Continental Congress.