Why do the people who claim to be closest to God kill one another?

I am referring to the people of Israel and Afganistan, the Jews and the Christians and the Muslims. They all seem to kill each other in the name of God who represents good. Also on that topic, why does people of the Muslim religion always want to destroy the United States? What is the real story behind that? I fully respect people of all religions, if I am offending anybody I apologize, I am just looking for answers.