Preheat the oven to 400 degrees F (200 degrees C). Spray a 9x13-inch glass baking dish with cooking spray.
Stir tomatoes, water, garlic, and stuffing mix in a large bowl; set aside to soften
Toss cubed chicken with salt in a large bowl; transfer onto the bottom of the baking dish. Sprinkle cheese and Italian seasoning on top of chicken. Spread the softened stuffing mixture on top.
Bake uncovered until chicken is cooked through and casserole is golden brown on top, about 30 minutes.