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 heat until shimmering.
Season the chicken cutlets with salt and pepper, then brown in the hot oil 2–3 minutes per side until cooked through; remove and set aside to rest.
Sauté the diced onion and diced red and green bell peppers in the same pot for 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 and shake to loosen any sauce, then add the contents to the pot and stir to combine.
Cut the browned chicken into bite-size pieces and add it back to the sauce.
Taste and adjust seasoning with salt and pepper as needed, then add the drained spaghetti and grated cheddar; toss until pasta is fully coated in the sauce.
If the sauce becomes too thick while resting, add small splashes of chicken broth or milk and stir until you reach the desired consistency.
Sprinkle with chopped cilantro if using and serve immediately.