QUINCY - The Bush administration is as slow to respond to a host of pressing demands on the nation’s economy as it was in responding to Hurricane Katrina last year, Sen. John Kerry told a breakfast meeting of the South Shore Chamber of Commerce today. ‘‘Katrina underscores lack of preparation, unpreparedness, despite all the warnings,’’ Kerry told a group gathered at the Quincy Marriott Hotel. ‘‘Katrina stripped away the confidence, the veneer that had cloaked this administration for a period of time, and people began to see a whole series of choices that have been wrong.’’ Kerry praised South Shore...