The titular question may seem like an odd one, especially for orthodox Christians. Orthodox Christians have always affirmed that Jesus is God, so why even ask the question if “God is Jesus” is correct? Of course Jesus is God, so God is Jesus, right? Well, perhaps things are not so clear.
First, we must ask ourselves what God is. He is a triune being; he is one being in three distinct persons. This generic formulation is common to all orthodox Christians. Next, we must ask ourselves the following: in what sense is it true to say “Jesus is God”?
Here we must distinguish between two different kinds of “is” statements: the “is” of identity and the “is” of predication. As we shall see, there are even sub-types of these kinds of “is” statements. What does it mean for something to be the “is” of identity? Roughly, something is identical with something else just in the case all of its essential properties are shared between the two. So, take “Mark Twain” and “Samuel Clemens.” There are no properties had by Mark Twain (the individual, not the proper name) not also had by Samuel Clemens. As a result, we say Mark Twain is identical to Samuel Clemens; Mark Twain just is Samuel Clemens.
Now the statement “Jesus is God” is fundamentally true for Christians. But is this the “is” of identity? It would seem that it is not. Why not? Because one of the features of identity is that it is transitive. For math majors out there, you’ll note that if A=B, and B=C, then, by the transitive property, A=C. The same exact principle applies to identity statements (in fact, it can be said that the mathematical principle is derived from this philosophical principle).
If that is true, then if the individual persons of the Trinity hold the “is” in the statement “is God” as one of identity, then a problem presents itself. “The Father is God,” “Jesus is God,” and “the Spirit is God,” are all identity statements. But that means the Father is the Son, the Son is the Spirit, and the Father is the Spirit. And surely no orthodox formulation of the Trinity concedes this, inasmuch as this is just denying that there even is a Trinity. So it cannot be the case that the statement “Jesus is God” is the “is” of identity.
That leaves us with the “is” of predication. There are two sub-types of predication: essential and accidental. Essential predication is that without which something would not be what it is; it is a property that is essential to that thing being what it is. So, for example, in the statement, “Socrates is a human,” the property of being human is an essential one; it is the “is” of essential predication, because Socrates couldn’t be who he is without being human. Accidental predication is a property that someone has but could have lacked and still could have been who they are. An example would be having the property of having n number of hairs, where n stands for the number of hairs on your head. Surely you are still you even when a single strand of hair falls out.
The predicative “is” we want here, however, will be essential predication. The statement “Jesus is God” will mean something more like “Jesus is deity,” or “Jesus is divine,” or “Jesus has divinity” (if we’re translating into properties). This now brings us to our question: is God Jesus? Let’s examine the two senses of “is.”
First, let us explore identity. I think the answer is clearly “no,” for precisely the same reasons outlined above. We do not want to collapse into modalism, and we do not exhaust what it means to speak of God when we speak of Jesus. But what about of predication? That answer also seems to be “no,” for we do not want to say that being Jesus is a property of God. Or is it?
It does seem that God has the essential predicate of being triune, and Jesus is an essential part of that (you cannot have the being that Christians refer to without Jesus). So, is God Jesus? Not in an identity statement. Is God Jesus? Yes, in that Jesus is a necessary person in the Trinity. But no, in that God is not merely Jesus. He is, necessarily, Father, Son, and Spirit, and these three are one in being, though distinct in persons.
 It’s important to note here that we’re not yet fleshing out varying models of the Trinity, or attempting to answer questions about what it means to be a person, etc., so that literally all orthodox Christians should be able to agree with this statement.
 And we would not want to say this is the “is” of identity, of course, because Socrates is not identical with humanness; we are not all just instantiations of Socrates.