Cook spaghetti according to package directions; drain and set aside
Cook chicken breasts or thighs until fully done; shred or dice
Heat a skillet over medium heat and sauté chopped onion, bell pepper, and garlic until softened
Add cream of chicken soup, diced tomatoes with green chilies, chicken broth, salt, black pepper, paprika, and cayenne if desired
Stir in shredded cheese until melted
Add cooked chicken and spaghetti to the sauce
Mix until evenly coated
Transfer to a baking dish if desired
Top with more cheese
Bake at 350°F for 20 to 25 minutes until hot and bubbly
Serve warm