One big impact of American law is that derives from the country's system of republican democracy, in which power is vested in the people and their elected representatives rather than in a monarch. So the laws that exist in this country are created by people we are empowered to elect or to vote out of office. Those laws are enforced and interpreted by judges, some of whom are elected by voters and some of whom are appointed by representatives who are accountable to the American people for those appointments. Other laws are directly voted on by the people themselves; these laws are called referendums. We also have the power to interpret laws ourselves when we serve on juries.
So one impact the law of the U.S. has had on American society is that it empowers the people with the responsibility and rights that comes with regulating their own community. This is mostly a very positive thing, as it endows a society based on political freedom, though it has also given people the power to oppress other people (by creating laws, for instance, that deprive certain groups of people of rights).
