In claiming that he was on a mission from God, Bush was using the God Brand. For millions of believers around the world the God Brand is easily recognized and accepted on its face value. American leaders consciously use the God Brand whenever they make it clear that they believe in God. And in some states there are laws prohibiting atheists from seeking certain political positions in local governments.
Would Bush or any politician dare stand in front of an image of Satan and declare that he was on a mission from the devil?
God is associated with goodness, love, mercy, justice, freedom, morality, family, etc. So politicians try to create an idealized image of themselves centered on principles that voters associate with the God Brand. Being successful at this can go a long way in the US toward reaching fund raising goals and garnering predictable support from the religious right and perhaps religious moderates.
