Combine first 8 ingredients in large saucepan; bring to a boil over medium heat. Reduce heat and simmer until potatoes are tender. Stir in ground beef and 2 cups milk.
Whisk together flour and remaining milk in a small bowl until smooth; gradually whisk into soup. Bring to a boil; cook 2 minutes or until thick and bubbly, stirring constantly. Reduce heat; add cheese and stir until melted. Add cayenne pepper, if desired. Top with bacon just before serving.