The irony is that HP does contain a lot of Christian imagery--Rowling is Christian, culturally if nothing else, and she's not exactly prone to examining her own biases and assumptions. She put in a lot of what she must have considered "normal" or "natural" symbolism and plot beats, and that wound up being Christian (e.g. snakes being evil, heroism via self-sacrifice, etc.). But she's no C.S. Lewis--she's not doing it on purpose, and the allegories are far from elegant.
Oh, absolutely! J.K.’s Christian faith most definitely influenced her books -- I think anyone would be foolish to argue otherwise. And I personally think that there were times where it was more purposeful than others -- sure, maybe her choice of associating the villain’s Hogwarts house, Slytherin, with snakes could’ve been inspired by the Bible, but snakes being associated with evil in the Western World isn’t just because of the Bible, it’s a trope that has become part of our cultural osmosis, like the tropes of Beauty and the Beast or love conquering all. Yet it’s pretty clear that Harry dying and then returning to life after selflessly sacrificing himself for everyone else was influenced by the Christian tradition, even if the J-Man was not the first or only deity to do that. But I maintain that it is still only one influence of many on J.K.’s work -- other things were the books she loved as a child, historical events and figures, traditional folklore and fairy tales, and even her own life. And that is what makes Harry Potter feel so personal and unique -- if it was just a beat-for-beat rehash of Biblical tradition, I don’t think it’d be half as popular as it was. Even The Chronicles of Narnia, which are more blatantly about Christ, do more than just “smuggle Christian theology” -- they were also likely affected by C.S. Lewis’s experiences during his service in the first World War, his love of creature comforts, his love of European fairy tales and folklore, and the people in his life. Aslan may = Jesus, but there is a lot more to Narnia’s appeal than just him. (I also must laugh at Granger listing The Lord of the Rings as a book that “smuggles Christian theology” as if it was Tolkien’s intention -- Tolkien apparently despised all forms of allegory like the kind Granger proposes. Even if you could read Christian faith or anything else into his work, Tolkien insisted that one never presume it was done purposefully by him.)