Lonnie G. Bunch III, the secretary of the Smithsonian Institution, knows well the complaints from some ( including this presidential administration ) that his museums focus too much on what is painful or ugly about the country’s history at the expense of what might be hopeful or uplifting about it. But as he sees it, the two aren’t mutually exclusive. “How do you understand a nation if you don’t look at all the challenges a nation has faced?” he asks in The American Experiment . “A great nation doesn’t run from its past, doesn’t hide from its past, but looks at it, learns from it and has been made better by that past.” The American Experiment The Bottom Line Dignified and intelligent, if a bit frustrating.…