Preheat the oven to 350°F (175°C). Lightly spray a 9x13-inch baking dish with non-stick cooking spray.

In a large bowl, combine the shredded chicken, softened cream cheese, 1 cup of shredded Mexican cheese blend, and garlic powder. Stir until the cream cheese is fully distributed and the mixture is thick and cohesive.

Spoon about 1/3 cup of the chicken filling into the center of each tortilla. Roll tightly and place seam-side down in the prepared baking dish, packing the enchiladas snugly together.

In a skillet over medium heat, melt the butter. Whisk in the flour and cook for 1 minute, stirring constantly. Gradually whisk in the chicken broth in a slow, steady stream. Stir in the taco seasoning and simmer for 3 to 4 minutes, stirring frequently, until the sauce thickens and coats the back of a spoon.

Remove the skillet from heat. Stir in the sour cream and diced green chilies until the sauce is smooth and creamy.

Pour the sauce evenly over the enchiladas, ensuring it reaches the edges and covers the ends of the tortillas. Scatter the remaining 1 cup of shredded cheese over the top.

Bake uncovered for 20 to 25 minutes until the sauce is bubbling around the edges and the cheese is melted and beginning to turn golden.

Let the dish rest for 5 minutes before serving. Top with shredded lettuce, pico de gallo, and sour cream if desired.