The United States has a government spending of 35% of GDP, in contrast to most advanced industrialized countries, whose government spending as percentage of GDP is over 40% on average.
Two main factors can account for this difference:
The constitution of the United States limits the scope of the federal government. The federal government can only do what it is explicitely allowed to do, and anything else is left to the states. Besides, the constitution provides protection of civil rights against government intervention, the reason why totalitarianism and dictatorship have never took hold in the U.S.
The United States was founded on the principles of economic liberalism. Government intervention in the economy is relatively low when compared to other countries such as France or Germany. Free trade, free enterprise and private property are actively promoted in the U.S., and these ideas are popular among most of the American population.
