The reasons can be found in the Bible. According to the Old Testament, that is the land God promised to His chosen people, Israel, and where much of God´s actions and messages took place and got spread. And that´s the land where Jesus Christ was born, where he lived and preached the good news of Gospel. That´s the land of Jesus´passion, death and resurrection. This explains its great relevance to Christians.
A Representative Democracy is a system of government where all eligible citizens vote on representatives to pass laws for them. An example is the U.S., where we elect a president, members of the Congress, local and state officials.