1. In a large pot, brown the ground beef over medium heat. Drain any excess fat.
2. Add the diced potatoes, onion, and garlic to the pot and cook until the vegetables are slightly softened.
3. Stir in the beef broth, Italian sauce, diced tomatoes, Worcestershire sauce, Italian seasoning, bay leaf, crushed red pepper flakes, salt, and pepper.
4. Simmer the soup for about 20 minutes, then add the thawed mixed vegetables and continue cooking until all the vegetables are tender.
5. Discard the bay leaf before serving. Adjust seasoning if needed.