There is a museum at the former site of the Gestapo headquarters in Berlin.  It is searing and frank: a history of the relationship of the Nazi party and the people of Berlin, telling a story of the way ordinary Germans made Hitler’s rise possible. Berliners flock to it. When I visited, the line of people shuffling past the informational panels was three or four deep, everyone meditating on this awful indictment of their grandparents’ generation.

There may be such museums in the United States, but I’ve never seen one. I’m more familiar with museums like the one memorializing the bombing of the Murrah Federal Building in Oklahoma City, where two domestic terrorists who despised the U.S. federal government killed 168 people, including 19 children in daycare. Unlike the museum in Berlin, the Oklahoma City museum is meant to be uplifting: Heroic first responders rush toward the explosion. A doctor performs makeshift surgery with a pocket knife. Around one corner, an authentic pile of rubble betokening the awesome power of the blast. Around the next, a miracle—the Bible that emerged unscathed.

Other sections narrate a thrilling police procedural: the truck axle thrown three blocks clear of the blast, whose miniscule identification number allowed intrepid investigators to uncover where Timothy McVeigh had rented the truck he turned into a bomb. The officer who, in an extraordinary coincidence, pulled over the getaway car because of its missing license plate and apprehended the sullen young man in the “Sic Semper Tyrannis” T-shirt. The arrest, the trial—justice.

Of course, the museum also tells the story of how Oklahoma “came together.” It almost frames bombing as a blessing. “Caring Communities Provide Safe Havens,” one panel read, above a picture of a church.

I saw the word “terrorism” only once, in a self-congratulatory text about how initial suspicions of “Muslim terrorists” were overcome, fair-minded Americans turning their rage on a corn-fed American boy instead: another blessing, this opportunity to prove that America was not racist. There was no mention of right-wing talk-radio host G. Gordon Liddy advising his listeners the previous year to confront agents of the Bureau of Alcohol, Tobacco and Fireams: “Go for a head shot; they’re going to be wearing bulletproof vests.” Or Newt Gingrich’s Republican revolutionaries taking over Congress via rhetoric depicting the federal government as an alien occupying army. Or Jesse Helms informing President Bill Clinton that if he visited North Carolina, he should bring bodyguards.

A political cartoon on display depicted someone asking, “How many hurt?” The answer: “260 million Americans”—the entire U.S. population at the time. The implication, of course, is that no one except four people—one duly executed by lethal injection, another in jail for the rest of his life, a third sentenced to 12 years and a fourth granted immunity—had anything to do with creating the political context of antigovernment rage that made the bombing possible.

This denial is how a childlike nation gets past trauma. It demonstrates how unprepared our nation is for the trauma about to be visited upon it. ...