Heat a large skillet over medium-high heat and add olive oil. Sauté onion and bell pepper until translucent, about 3-5 minutes. Turn the heat to medium and stir in taco seasoning, fire roasted tomatoes, cream of mushroom soup, cream of chicken soup and chicken broth. Once the mixture comes to a simmer, fold in American cheese and 1 cup of the cheddar cheese. Stir until it’s a cohesive mix, then fold in the chicken and spaghetti.