How would America react to a future terrorist attack? Would the country come together to combat its adversaries, or would it pull further apart? Perhaps we will never have to confront the question, you say. Perhaps our good luck will hold, or our intelligence will detect all the plots and plotters, or the terrorists will conclude that America is so divided anyway, why do anything that might unite the country. Maybe things will turn out that way, but a prudent person wouldn't bet on it. The British car bomb plots uncovered this past week remind Americans of their vulnerability to terrorist attack, wherever they live. Muslims have mostly been killing other Muslims in Iraq and Afghanistan, but that imploding jihad won't continue forever. What's ahead is a phenomenon that an intelligence official described several years ago as "bleed-out, in which the suicide bombers of Baghdad look outward for targets--to Europe and America. A chilling measure of Muslim anger is that several of the suspected bomb plotters arrested by the British are medical doctors. What kind of rage would lead a physician trained in the healing arts to pack together nails, explosives and propane gas in a mix that would shatter bones and rip apart human flesh? This is a revolt of the privileged, the uprooted, the disconnected. It speaks of self-mutilation, as much as mayhem against others. What happens when the bleed-out reaches America? Intelligence officials talk about this threat of future terrorist attacks in terms of "when, not "if. How would the country react? The united and resolute response to 9/11 has become part of America's national identity--the flags on every house, the nation standing together with the president and the mayor of New York at Ground Zero. But what about now? Based on the tone of the national debate today, it seems likely that the American public would react angrily--but not just at the terrorists. Liberals would blame the Bush administration for making America a more vulnerable target. Didn't the war in Iraq inflame Muslim terrorists around the world? Wouldn't we have been safer today if we had focused on Al-Qaeda in Afghanistan, rather than embarking on a costly war that has sapped the military and CIA and added to America's enemies? These arguments aren't imaginary: We hear them every day, almost as rehearsals for the post-attack finger-pointing. And how would conservatives respond? They would blame liberals who, in their view, have weakened America's anti-terrorist defenses. Couldn't we have stopped the bombers if critics hadn't exposed the National Security Agency's secret wiretapping program? Wouldn't aggressive Central Intelligence Agency interrogation techniques have yielded more intelligence that might have prevented the tragedy? Didn't congressional demands to withdraw from Iraq embolden the terrorists? I can hear the voices on talk radio and cable news right now. America's political disharmony is scary. But so is the lack of practical preparation for the next attack. With all the emotional discussion of 9/11--all the commissions and studies and new federal agencies--you might expect that we had gotten that part right. But we haven't. Despite spending billions of dollars on supposed bio-defense, the United States is still woefully unprepared for a biological attack. If you doubt it, listen to Dr. Tara O'Toole, director of the Center for Biosecurity in Baltimore and one of the nation's leading experts on the problem. "More than five years after the anthrax mailings, the US still lacks a coherent plan for conduct of operations to guide the health care sector's response to mass-casualty care in the event of a bioterrorist attack or other large-scale catastrophe, she told a House committee in March. And nuclear terrorism? Despite repeated warnings by intelligence officials about this threat, the US still is unprepared to detect or counter these weapons. Listen to Fred Ikle, a former undersecretary of defense and the author of "Annihilation from Within, a grim assessment of America's vulnerability to attack. "To detect smuggled uranium bombs, we still lack the right tools, Ikle said in a recent interview. He noted that the Homeland Security Department has not developed such "active interrogation devices because of possible risk to bystanders, and the Pentagon's Defense Threat Reduction Agency hasn't done so because of inadequate funding. In a politically healthy nation, the news from Britain would have a galvanizing effect. Politicians and the public would pull together and take appropriate steps to prepare for future terrorist attacks on America. There was a moment of shared purpose after 9/11. It's frightening how totally that mood of national unity has dissipated. I can think of lots of people to blame for the current polarization, but that's not the point. The point is to get serious, and get ready. Syndicated columnistDavid Ignatius is published regularly by THE DAILY STAR.