In a large skillet over medium-high heat, cook the ground beef, onion, and bell pepper for 5 to 7 minutes, until the beef is no longer pink. Drain excess grease.
Stir in the garlic, taco seasoning, chili powder, and cumin. Cook 30 seconds to 1 minute, until fragrant.
Add the beef mixture to a greased 6-quart slow cooker. Stir in the diced tomatoes with green chiles, tomato sauce, black beans, corn, 2 cups beef broth, salt, and pepper.
Cover and cook on LOW for 3 to 4 hours or on HIGH for 2 hours.
Stir in the cream cheese cubes. Cover and cook on HIGH for 10 to 15 minutes, then stir until the sauce is creamy.
Spread the dry spaghetti over the top and gently press it into the sauce. Add up to ½ cup more broth if needed so the pasta is mostly submerged.
Cover and cook on HIGH for 20 to 30 minutes, stirring gently once or twice, until the spaghetti is just al dente.
Sprinkle 1 cup shredded cheese over the top. Cover and let sit on WARM for 5 to 10 minutes, until melted. Stir gently, then top with the remaining ½ cup cheese and serve.