Bring a large pot of salted water to a boil and cook the spaghetti according to package directions until al dente; drain and set aside.
Return the empty pot to medium heat, add the olive oil, and swirl to coat the bottom.
Season the chicken cutlets with salt and pepper and brown in the oil 2–3 minutes per side until cooked through; remove and set aside to rest.
In the same pot, sauté the diced onion and diced red and green bell peppers 4–5 minutes until mostly tender.
Stir in the diced green chiles, alfredo sauce, cumin, chili powder, and garlic powder.
Pour 1 cup chicken broth into the empty alfredo jar, replace the lid, shake to rinse out any remaining sauce, and add the contents to the pot.
Cut the browned chicken into bite-size pieces and return them to the pot; taste and adjust seasoning with salt and pepper as needed.
Add the cooked spaghetti and grated cheddar to the sauce and toss until the pasta is fully coated; if the sauce thickens too much, add small splashes of chicken broth or milk to reach the desired consistency.
Sprinkle with chopped cilantro if using and serve immediately.