Roots of US government
The present United States government was formed by several colonial, and British practices. Without any of the the below occurrences. United States culture and government would be drastically different.
The Ten Commandments, or the Decalogue, are a set of laws which were given to Moses by God. In several controversies over the legality of displaying the Ten Commandments on government property, and especially outside courthouses, the influence of the Ten Commandments on US law becomes relevant as proponents of the displays argue that these commandments form part of the foundation of the US legal system. 
The Magna Carta was written in 1215, and was used to limit the power of the King. It distributed more power to the people, and granted us the right of a jury among peers. Today, we use the Magna Carta ideals to limit the power of the president, and uphold the 6th amendment in the Bill of Rights.
The Parliament is the central governing body of England. The United States derives its bicameral Congress from this, and adopts the practice of using a governing body to use checks and balances on an executive.
English Bill of Rights
The English Bill of Rights was similar to the United State's bill of rights. It acknowledged the natural rights of the people, and made it mandatory for the King to seek Parliament's approval before making decisions. Our idea of a Bill of Rights is based on this premise.
John Peter Zenger was a newspaper publisher who printed material critical of the royal governor. He was put on trial for libel, but a jury found him innocent. From this we derive our first amendment rights of freedom of speech and freedom of the press.