A. You think that’s an easy question, don’t you? You think the answer is simply that God does not have a religion – how could He? – and though He has a special relationship with the Jewish people, He is the Creator of the whole universe, and every one of the peoples enjoys His concern.
The Tanach says, “’’Are you not as the children of the Ethiopians to me, O children of Israel?’, says the Lord: ‘Have I not brought up Israel out of the land of Egypt, and the Philistines from Kaphtor, and Aram from Kir?’” (Amos 9:7).
But in a sense it might still be said that God is Jewish. The rabbis say that in order to show Israel how to pray, God (so to speak) puts on a tallit and acts as a chazan. Elsewhere it is said that Israel has tefillin that celebrate the uniqueness of God and God has, so to speak, tefillin that celebrate the uniqueness of Israel.
Rashi’s comment on the first line of the Shema looks forward to the day when HaShem, who is at this stage of history our God, will in time to come be the God of all humankind. That does not mean to say that God is a member of the Jewish people, but that other peoples are yet to acknowledge and worship Him.