In Genesis 12:3, God promises Abraham that, "I will bless those who bless you, and I will curse him who curses you." The "you" employed here is a plural, referring to Abraham and his descendants, that is Israel. To a dispensationalist, therefore, Genesis 12:3 practically commands philo-Semitism and Zionism. Genesis 12:3 is Christian Zionism in a nutshell.
This then, is the REAL reason why many American Christian evangelicals support Israel. They believe it is a Gd-given commandment. I just thought you should know.