If you’re an American, your favorite movie is probably “Casablanca.” That’s what the best surveys show. Facing a growing Nazi threat, Humphrey Bogart’s Rick Blaine gets to us. “I stick my neck out for nobody,” Rick says when the collaborationist local police chief arrests one of the regulars at Rick’s Cafe, mainly to impress a newly arrived SS officer. It’s only when there’s talk of attacking America that our hero begins to show the stuff he’s made of. “Can you imagine us in London?” a Nazi major asks Rick. “When you get there, ask me,” Rick replies. “How about New York?” the Nazi persists. “Well, there are certain sections of New York, Major, that I wouldn’t advise you to try to invade.”

Now our guy is showing his teeth. When his ideals, his love and his country are on the line, Rick will commit himself to the war against an evil he now sees in his face.

Like the hero of “Casablanca” we are not a country impressed by generals in epaulets and high-peaked hats. Our officers don’t strut. Our troops don’t goose-step. But while we reject the dandified haberdashery of war, we will strike back ferociously when attacked, when someone or something we value dearly is threatened.

It’s a tradition with roots older than the Republic. The rattlesnake of don’t tread on me is an ancient American icon. “The Rattle-Snake is solitary, and associates with her kind only when it is necessary for their preservation,” said Benjamin Franklin. This marks our instinct to ally with others when faced with a common danger. During the American Revolution, the artist Benjamin West was asked by King George III what he thought George Washington would do after the war. When West answered that Washington would return to his Virginia farm, the king replied, “If he does that, he will be the greatest man in the world.” When he left the presidency after two terms, Washington set an important standard: there was a power and majesty in humility.

Part of this tradition is geography; we are a relatively contained country. Part was our recoiling from what Jefferson called the “entangling alliances” of European quarrels. “I want an American character that the powers of Europe may be convinced we act for ourselves and not the others,” Washington had warned in his farewell.

Living in isolation sometimes exacted a high price: the middle of the 20th century might have turned out better, with more lives saved, if America had been quicker to engage the dictators.

That is the perpetual American dilemma, one made urgent by the Bush administration’s policy toward Iraq. When is reluctance a good thing, and when is it just wishful thinking? In the world after 9-11, Bush called us to arms. “The nation is peaceful but fierce when stirred to anger,” the president said, sounding like a consummate rattlesnake. Sadly, a campaign focused on eradicating the terrorist network behind September 11 soon began to show undeniable signs of mission creep. From a war to destroy Al Qaeda, our target expanded to any international terrorist group. Then we pushed on to the “axis of evil”–Iraq, Iran and North Korea. This is mission creep with a vengeance. We now risk moving from reluctant warriors to bullies spoiling for a fight.

I worry that this change in course threatens us with dangerous consequences. Will America still be guided by its role as a reluctant warrior in this century? Or will the reality of America’s colossal military power overwhelm the fine instincts of our history? The polls show we fear American casualties in a fight for Baghdad but also worry about inflicting heavy casualties on the civilian defenders. We know that a bloodbath could stir an anti-American backlash we might never survive.

It is not easy being an American–it isn’t supposed to be. Yes, there are really bad guys out there, arming themselves with terrible weapons. And like Rick, we may find ourselves rightly dragged into a just war. But we should never forget that the best part of our history teaches us to do so carefully, even prayerfully. “It’s still the same old story,” Sam sings in “Casablanca, “a fight for love and glory…” Let’s just make sure it’s the right fight in the right place for the right reasons.