Preheat the oven to 425°F and position a rack 6 inches from the broiler.

Place the chicken on a rimmed baking sheet and bake until heated through, about 20 minutes.

In a bowl, mix 2 tablespoons hot sauce, melted butter, and 1 teaspoon ranch seasoning.

Cut the chicken into ½-inch pieces and toss in the hot sauce mixture to coat.

Meanwhile, in a 12-inch broiler-safe skillet, bring the water and milk to a boil over medium-high heat.

Stir in the macaroni, reduce heat to medium-low, cover, and cook until al dente, about 5 minutes, stirring once halfway through.

Stir in American cheese, 1 tablespoon hot sauce, and the remaining 1 teaspoon ranch seasoning until the cheese melts, about 2 minutes.

Remove from heat and stir in cheddar until fully melted, about 2 minutes.

Heat the broiler.

Evenly distribute the chicken over the macaroni and broil until lightly browned, about 3 minutes.

Drizzle with the remaining 2 tablespoons hot sauce and sprinkle with scallions.

Serve immediately.