Preheat the oven to 350°F (175°C). Lightly spray a 9 x 13-inch 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; drain and set aside.
While the pasta cooks, heat a large skillet over medium. Add the ground beef, diced onion, and diced green bell pepper. Cook 8–10 minutes, stirring and breaking up the beef, until beef is browned and vegetables are softened.
Add the minced garlic and cook 1 minute more until fragrant. Drain excess grease from the skillet and transfer the meat mixture to a large mixing bowl.
To the bowl with the beef, add the undrained diced tomatoes, cream of mushroom soup, chicken broth, corn, peas, chili powder, salt, and pepper. Stir to combine.
Add the cooked spaghetti to the beef and vegetable mixture and toss well to coat, using tongs or a spaghetti server if needed.
Transfer the combined spaghetti mixture to the prepared casserole dish and sprinkle the shredded cheddar evenly over the top.
Bake for 15–20 minutes, or until the cheese is fully melted and the casserole is heated through. Serve warm.