Preheat the oven to 350°F (175°C). Lightly spray a 9 x 13 casserole dish with cooking oil and set aside.
Bring a large pot of salted water to a boil. Add the spaghetti and cook 8–11 minutes or until al dente according to package directions, then drain and set aside.
While the pasta cooks, heat a large skillet over medium heat. Add the ground beef, diced onion, and diced green bell pepper and cook 8–10 minutes, stirring to break up the meat, until beef is browned and vegetables are softened.
Add the minced garlic and cook 1 minute until fragrant. Drain excess grease from the skillet and transfer the meat mixture to a large mixing bowl.
To the bowl with the meat, add the undrained diced tomatoes, cream of mushroom soup, chicken broth, corn, peas, chili powder, salt, and pepper. Stir until combined.
Add the cooked spaghetti to the meat and vegetable mixture and toss well to combine using tongs or a pasta server.
Transfer the combined spaghetti mixture to the prepared casserole dish and sprinkle the shredded cheddar evenly over the top.
Bake in the preheated oven 15–20 minutes, or until the cheese is fully melted. Remove from oven and serve.
