Cook spaghetti as directed on package. Drain; cover to keep warm.
Meanwhile, in 12-inch nonstick skillet, heat oil over medium heat. Add onion and bell pepper; cook 3 to 4 minutes, stirring occasionally, until tender. Remove from skillet. Add ground beef to same skillet; cook until thoroughly cooked, stirring frequently. Drain.
Add onion and bell pepper to ground beef; mix well. Add sugar, taco seasoning mix, tomatoes, tomato sauce, corn and mushrooms; mix well. Heat to boiling. Reduce heat to low; simmer 5 minutes, stirring occasionally. Serve over spaghetti. Sprinkle with cheese.