The American political highway is always circuitous, a tangled web of regional and ideological intrigue, seldom tranquil and most often agonizing. There are few exceptions in our nation’s history.

One would think going to war against Nazi Germany and its canon of diabolic beliefs would be the exception.

But no. It took more than two years of bitter national debate before a hesitant President Franklin Roosevelt and a recalcitrant Congress overcame a vocal and well-organized minority to lead the nation into war. And then it came only after the Japanese sneak attack on our Pacific Fleet stunned the nation into action.

That is the story of Lynne Olson’s “Those Angry Days”: The momentous national conflict of the period between the spring of 1939 when Hitler seized all of Czechoslovakia and Dec. 7, 1941, the day the debate abruptly ended.

Olson is a historian with the heart of a storyteller. She understands the need for protagonists and human conflict in the writing of history. Every chapter of this book – like her last work, “Citizens of London” – moves the narrative briskly forward.

At first, the storyline seems simple enough. President Roosevelt will push an isolationist nation, stung by the failures of post-World War I Europe, into rescuing Britain and France from Nazi tyranny. American aviation hero Charles Lindbergh, strongly pro-German – some would say a Nazi sympathizer – will spend every drop of his star power to keep America from taking sides in this, another useless European war.

The two icons of prewar United States are set on a collision course.

To appreciate Lindbergh’s importance to this plot, one most understand the 1930s. Lindbergh, the tall, blond, boyish Midwestern flier was everything Americans dreamed of in a hero. He was Elvis Presley and Jack Kennedy, all rolled into one flying suit. His words influenced millions.

But the simple plot thickens when the Nazi military machine rolls into the Low Countries, and the French sue for peace, leaving England alone to defend Western democracy.

The wildly popular president, still stung by a humiliating defeat at the hands of a coalition of conservative Democrats and solid Republicans over expanding the Supreme Court, shows signs of timidity and indecision for the first time in his career.

He is torn between a desire to rush to the aid of Great Britain and the Western Allies, and his ambition to seek an unprecedented third term, he hopes by national acclamation. The president reasons he mustn’t get out ahead of his voters.

At the same time, the matinee idol Lindbergh, once he is thrust into the public policy spotlight, proves to be a stubborn, prejudiced and outspoken loner, lacking in human empathy. Today, we would say of Lindbergh, it was his way or the highway.

Olson captures the hysteria and the color of a bygone era when the newspapers were the people’s Facebook and the Western Union telegram was their Twitter.

There were the syndicated newspaper columnists competing for readers, and the fledgling radio networks, vying for the attention of the American family, which listened to live political speeches broadcast into their living rooms.

The new weekly magazines, tried each with their own points of view – today we call that a biased media and think it’s a 21st century phenomenon – mirrored the great chasm that existed between the interventionists and the isolationists.

It was a time of Fifth Columnists, FBI dossiers and the wiretapping of foreign diplomats and the Americans they contacted. Both England and Germany had active propaganda machines operating inside our borders.

Talk about political conflict! Some of it was regional, some ideological, much of it economic and lots of it ethnic. But each side believed strongly in its cause, often based on a few catchphrases heard on the radio or read in the newspaper.

Olson describes in electrifying detail the thousands standing daily in Times Square, staring up at the illuminated news bulletins on Times Tower as the Nazi Blitzkrieg crushed Denmark, then Norway, Holland, Belgium and finally France, trapping the British Expeditionary Force on the beach at Dunkirk.

As we move closer to Pearl Harbor, the once simple plot breaks down. Lindbergh shows himself to be politically myopic. The more he talks, the more he self-destructs, culminating in his September 1941 speech in Des Moines, Iowa, which bared his openly anti-Semitic sentiments to a national radio audience estimated at more than a million listeners. It was universally disavowed. Even his staunchest supporters were outraged.

Lindbergh’s wife, Anne, who initially was taken in by Hitler’s charm before admitting she had been conned, later insisted her husband was not prejudiced but was “tone-deaf to nuance and the sensibilities of others.” Unlike Anne, Lindbergh never was able to admit he had been wrong about Nazism. Or anything else.

A socialist detractor, Norman Thomas, said: “I honestly don’t believe Lindbergh is an anti-Semite, but I think he is a great idiot.”

As the story line moves away from Lindbergh and deeper into Roosevelt, Olson takes us through the 1940 presidential campaign in which GOP challenger Wendell Willkie defies his party and comes out in favor of helping the Brits at all cost, even if it means Americans on the front lines. Meanwhile, the president, who vowed not to campaign for a third term, takes to the airwaves to criticize his opponent in the tightening race.

At one point in what became a mud-fest, Roosevelt aides agreed to keep secret Willkie’s extramarital affair if Willkie’s people promised not to raise Henry Wallace’s history of mental instability. Wallace was Roosevelt’s handpicked running mate.

It often is lost in history that the 1940 election was the closest presidential election in a quarter century. Willkie, who would become more interventionist than many Democrats, eventually worked with Roosevelt on preparations for war, but he confided to his friends that he never trusted the president.

Author Olson, in defiance of conventional wisdom, argues Roosevelt did not use his political savvy to nudge America into World War II.

She insists the master political juggler fell way behind the American public and procrastinated through this period, unnerving not only Winston Churchill but Roosevelt’s own aides. The president, she claims, never gave up hope America could remain a noncombatant, while supplying the Allies with the materials needed to overcome the enemy.

In keeping with that premise, she dispels out of hand any Roosevelt complicity in Pearl Harbor.

In any event, Pearl Harbor and its aftermath seem to have lowered a curtain over the deep animosity and national divide in the years leading up to the U.S. entry into World War II.

Olson reminds us with this thrilling narrative – a page-turner – of just how bitterly conflicted we were as a nation until that Sunday morning of Dec. 7, 1941, the day on which the U.S. took a sharp turn toward world leadership and never looked back.

Those Angry Days: Roosevelt, Lindbergh and America’s Fight Over World War II, 1939-1941

By Lynne Olson

Random House

548 pages, $30

Edward Cuddihy is a former News managing editor.