Spray the inside of a 9-inch x 13-inch casserole dish with cooking spray and set aside.
In a large bowl, mix together the soup, sour cream, milk, green onions, 1/2 cup of each cheese, and 2 tablespoons of ranch mix until thoroughly combined.
Stir the chicken and 3/4 of the crumbled bacon into the sour cream mixture. Then pour the chicken mixture into the prepared baking dish and spread into an even layer.
Place the tater tots into a gallon-sized plastic bag and add 2 tablespoons of Ranch seasoning mix. Close the bag and shake the tater tots around gently to coat each one with seasoning.
Pour the tater tots out on top of the chicken mixture and spread them out into one even layer.
Baked the casserole for 40 minutes. Once the timer goes off, add the rest of the shredded cheese and remaining bacon over the top of the casserole. Bake for another 10 minutes.
Remove from the oven and sprinkle more green onions on top for garnish, if desired. Serve warm.