I have found that if you are having trouble thickening your potato soup add instant mashed potatoes to it until it gets to the consistency you want. This can also be a great opportunity to add flavor (such as loaded mashed potatoes)
In a large saucepan, cook bacon over medium heat until crisp. Using a slotted spoon remove to paper towels; drain.
Add the broth, vegetables, and seasonings. Bring to a boil. Reduce heat; cover and simmer for 15 minutes or until potatoes are tender. Combine flour and milk until smooth; add to soup. Bring to a boil; cook and stir for 2 minutes.
Add cheese; stir until cheese is melted and the soup is heated through. Garnish with green onions if desired.