Step 1: Cook the Spaghetti
Preheat your oven to 350°F (175°C). Cook the broken spaghetti in a large pot of salted boiling water according to package directions until al dente (it will cook more in the oven). Drain and set aside.

Step 2: Sauté the Vegetables
While the pasta cooks, heat the olive oil in a large skillet over medium-high heat. Add the diced bell peppers and onion. Cook for 6-8 minutes, until softened and beginning to caramelize. Add the minced garlic and cook for 1 more minute until fragrant.

Step 3: Create the Creamy Sauce
In the same skillet with the vegetables (or in a very large mixing bowl), combine the cream of chicken soup, undrained Ro-Tel tomatoes, barbecue sauce, chicken broth, sour cream, chili powder, cumin, smoked paprika, salt, and pepper. Stir until the mixture is smooth and well combined.

Step 4: Combine Everything
In an extra-large mixing bowl or the pot used for the pasta, combine the drained al dente spaghetti, the shredded chicken, the vegetable and sauce mixture, and 2 cups of the shredded Monterey Jack cheese. Stir gently but thoroughly until every strand of spaghetti is coated in the sauce and everything is evenly distributed.

Step 5: Assemble the Casserole
Lightly grease a 9×13-inch baking dish. Pour the spaghetti mixture into the dish, spreading it out into an even layer.

Step 6: Add the Cheese & Bacon Topping
Sprinkle the remaining 1 cup of Monterey Jack cheese and the 1 cup of shredded cheddar cheese evenly over the top of the casserole. Scatter the crumbled bacon evenly over the cheese.

Step 7: Bake to Bubbly Perfection
Cover the dish with aluminum foil (to prevent the cheese from burning) and bake for 20 minutes. Then, remove the foil and bake for an additional 15-20 minutes, or until the casserole is hot and bubbly throughout and the cheese on top is fully melted and just starting to get golden spots.

Step 8: Rest, Garnish, and Serve
Remove the casserole from the oven and let it rest for 10 minutes before serving. This allows it to set slightly for cleaner serving. Garnish with sliced green onions and fresh cilantro (if using). Serve hot, directly from the baking dish