Heat oven to 350°F. Mist a 9x13-inch baking dish with cooking spray.
Bring a large pot of salted water to a boil.
Cook spaghetti until just shy of al dente; drain and set aside.
Warm olive oil in a skillet over medium heat.
Sauté onion and bell pepper until tender, 5–6 minutes. Stir in garlic for 30 seconds.
Whisk in condensed soup, broth, and cream cheese until smooth and creamy.
Stir in tomatoes, 1.5 cups cheddar, salt, pepper, and paprika. Simmer 2 minutes.
Combine spaghetti, chicken, and sauce in a large bowl. Toss to coat evenly.
Spread mixture in the prepared dish. Top with remaining cheddar.
Bake until bubbly and lightly browned, 20–25 minutes. Rest 5 minutes.
Finish with parsley and serve warm.
Notes
Variation: Swap half the cheddar with Monterey Jack for extra melt. For heat, add a pinch of red pepper flakes. Storage: Refrigerate leftovers up to 4 days; reheat covered at 325°F with a splash of broth.This recipe is an original creation inspired by classic Easy Chicken Spaghetti Bake flavors. All ingredient ratios and instructions are independently developed.