Reading the horrified reactions to the bloody attack on the Tree of Life synagogue in Pittsburgh, one has the impression that the assault was carried out by a crazed individual operating from the most deranged fringe of America’s alt-right: a product of the brutal politics of Donald Trump and social media run amok. The fact is that, though America would dearly love to forget it, anti-Semitism has long been deeply embedded in the U.S.

In the Spring of 1942, the sociologist David Riesman described American anti-Semitism as "slightly below the boiling point."

Indeed, the despicable image of an American president slamming shut his country’s Southern border to desperate refugees fleeing the violence of their homeland is nothing new. The same tragic tale played out in the United States in the spring of 1939, when Franklin Roosevelt was President: U.S. authorities refused to let a ship, the St. Louis, loaded with more than 900 passengers, most of them Jews attempting to escape from Germany, refused to let them dock in the U.S.

Already forbidden from landing in Cuba, the ship’s German captain Gustav Schroder (not a Jew), circled off the coast of Florida, hoping for permission to enter the United States. But Secretary of State Cordell Hull advised President Franklin Roosevelt not to accept the Jews. Still determined to save his passengers, Captain Schröder considered running aground along the U.S. coast to allow the refugees to escape. But, again, acting on Cordell Hull's instructions, US Coast Guard vessels shadowed the ship and prevented such a move.

Also refused entry by Canada and Great Britain, Captain Schroder finally returned to Europe, but only after several European countries other than Germany agreed to accept a portion of the refugees. But Hitler still caught up with many of them: more than 250 of the St Louis passengers ultimately died in the Holocaust.

That was just one episode of America’s shameful role during World War II. "The Nazis were the murderers, but we were the all too passive accomplices." Such was the verdict of American historian, David Wyman, a Protestant, who, after years of the most thorough research, in 1984 produced an extremely disturbing book, "The Abandonment of the Jews" (Pantheon). Wyman’s findings have not been disputed. There have been similar books on the subject, documenting chapter and verse.

For instance, little Switzerland—charged with closing its borders to the Jews during WWII —in fact accepted as many Jewish refugees during the war — 21,000 — as did the vastly greater United States. That pitifully small number represented only 10 percent of the number who could have been legally admitted under U.S. immigration quotas at the time.

Tens of thousands of Jews were turned away or dissuaded from applying for visas by U.S. officials intent on keeping the inflow to a trickle.

It is clear that by the summer of 1942, Washington had confirmed accounts of Hitler's plan to exterminate the Jews. But, according to Mr. Wyman: "The American State Department and the British Foreign Office had no intention of rescuing large numbers of European Jews. On the contrary, they continually feared that Germany or other Axis nations might release tens of thousands of Jews into Allied hands. Any such exodus would have placed intense pressure on Britain to open Palestine and on the United States to take in more Jewish refugees — a situation the two great powers did not want to face. Consequently, their policies aimed at obstructing rescue possibilities and dampening public pressures for government action.

.Incredibly, according to Mr. Wyman, Anthony Eden even opposed a joint plea from the Allies to Germany to release the Jews because of his fear that Germany might actually agree.

Strong popular pressure could have made a difference. Why wasn't it there? Anti-Semitism and anti-immigration attitudes were widespread in American society and entrenched in Congress. In the late 1930s, as Jews were scrambling to escape from Europe, a Roper poll showed that 70 to 85 percent of the American people opposed raising quotas to help Jewish refugees enter the United States.

Even more shocking, another set of polls taken in the years between 1938 and 1945 revealed that as much as 35 to 40 percent of the U.S. population was prepared to approve an anti-Jewish campaign in America. Only 30 percent would have opposed it, and the rest would have remained indifferent.

There was also the failure of the mass media — including newspapers like the New York Times — to publicize Holocaust news, even though the wire services and other sources made most of the information available early on.

Added to that were the near silence of the Christian churches and most of their leaders and the indifference of American political and intellectual nabobs.

One of the greatest American journalists of the day, Walter Lippmann, for instance, wrote not a single column about the Holocaust or the death camps.

As for President Franklin Roosevelt, according to Mr. Wyman, he did nothing about the mass murder for 14 months after first learning about it. And then he "moved only because he was confronted with political pressures he could not avoid and because his administration stood on the brink of a nasty scandal over its rescue policies."

Even most of America's Jewish leaders at the time were remiss, caught up in internal bickering, concerned about provoking anti-Semitism, more worried about establishing the state of Israel than saving Jews from the Holocaust.

It’s ironic how insistent we were after the war that the Germans recognize their shameful history—teach it in their schools, and so on. The French also have similarly felt obliged to confront their shameful willingness to collaborate in the Holocaust. As have the Swiss.

Americans and Canadians and Brits, meanwhile, have done their best to bury and try to forget.