Spray a 9x13 inch baking dish with nonstick cooking spray and cover the bottom with half a can of green enchilada sauce (about 5 ounces).
In a medium skillet, combine the shredded chicken, cream cheese, diced green chiles, garlic powder, chili powder, cumin, salt, and the remaining half of one can of green enchilada sauce. Cook the mixture until heated through.
In a bowl, combine the shredded Pepper Jack and shredded cheddar cheese. Set aside.
Spread ½ cup of enchilada sauce in the bottom of a 9x13 inch baking dish. Cut or tear the tortillas in half and line the bottom of the dish with 12 halves. Spread ⅓ of the chicken mixture and sprinkle with 1 cup of cheese. Repeat with two more layers, reserving ½ cup of shredded cheese. On top of the third layer, add 12 more tortilla halves and pour the second can of sauce over the top. Sprinkle with the remaining ½ cup shredded cheese.
Bake at 350 degrees for 30 - 35 minutes. Let the enchiladas rest for 10 minutes before serving.