Preheat the oven to 350°F. 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, breaking up the beef, until the meat is browned and the vegetables are softened.
Add the minced garlic to the skillet 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 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 combine using tongs or a spaghetti spoon.
Pour the combined spaghetti mixture into the prepared casserole dish. Evenly sprinkle the shredded cheddar over the top.
Bake for 15–20 minutes, until the cheese is fully melted. Remove from the oven and serve.