Preheat oven to 350 degrees. Add chicken to a stock pot and cover with water. Place it on the stove over medium-high heat. Stir in the chicken bouillon, black pepper, garlic powder, and onion powder.
Bring it to a low boil for 20 minutes. Once done, remove the chicken and place it in a bowl to cool down. Reserve the cooking liquid to use in the sauce. Once the chicken is cool enough, use your hands to shred it into large pieces, and set aside.
Fill a separate stock pot up with water and bring to a rapid boil. Add in the spaghetti noodles. Boil for 10 minutes- until they are al dente. Drain the water and rinse the noodles with cold water. Set them aside
Add olive oil to a large skillet or pot over medium heat and allow it to heat up for 2-3 minutes. Place the bell peppers in the oil and saute for 2 minute. Next add the garlic and saute for one minute (careful not to burn the garlic).
Pour the cream of mushroom and cream of chicken directly into the skillet. Fill the can up with the water the chicken cooked in (2 cans full total), and add it into the skillet.
Add in the seasoned salt, Italian seasoning, garlic powder, and black pepper. Use a whisk to mix it until fully combined and smooth.
Sprinkle in the 1/2 cup each of Mozzarella and cheddar cheese and stir it in until it is melted. Add in the chicken, and the spaghetti and gently mix it until combined.
Spray a 9x13 baking dish with non-stick cooking spray. Pour the spaghetti into the dish. Sprinkle the remaining cheese over the top of the pasta. Cover the dish with aluminum foil and bake for 15 minutes.
Remove the foil from the baking dish and put the oven on broil. Broil the chicken spaghetti for 5 minutes to brown the cheese. Keep a close eye on it so it does not burn.
Remove it from the oven and let it cool for for 5-7 minutes before serving.