If by "the Christian God" you mean the unchristian triune deity, I don't think I've ever heard or read of anyone suggesting that Einstein believed in any such being. But I wouldn't doubt that there are preachers in the evangelical/fundamentalist wing of Christendom who may have promulgated such an idea; that isn't as strange as some of the things that I've heard them pushing on TV and in their churches when I've attended with friends.
Einstein did not believe in a personal God. He could probably best be described as a Deist, as were most of the Founders of our nation such as George Washington, Thomas Jefferson, and James Madison. When asked by a prominent New York rabbi to expand on his concept of God, he replied in part: "I believe in Spinoza's God who reveals himself in the orderly harmony of what exists, not in a God who concerns himself with the fates and actions of human beings."