American society is dominated by middle force.Balance between liberalism (Left in U.S.politics) and conservatism (Right in U.S.politics) is somewhat kept.Liberal ideas,such as control of economy strengthened by government and social equity realized through "redistribution",have been somewhat in upper hand a little during Obama presidency.However,they are fiercely opposed by conservatives.As for relations between government and society,struggle between conservative tradition of "homogeneity" and liberal idea of "pluralism" is especially intense.On balance between national security and civil rights,conservative proposition regarding national security as top priority still dominates the whole society.In a longer period it is an irresistible that ideology in the U.S.will lean toward liberalism.