Leonard Dinnerstein, in his book Antisemitism in America, calls his chapter on WWII "Antisemitism at High Tide," due to the high levels of antisemitism during this era. He attributes this in hindsight to the natural hysteria and intolerance of minorities brought on by wartime as well as to preexisting desires for isolationism and staying out of the war. That said, this antisemitism simply built on preexisting sentiments from the 1920s-30s, which I discuss some aspects of here and here but which I'll sum up as being largely a combination of social antisemitism (not letting Jews into certain kinds of social venues, businesses, jobs, etc) and conspiracy theories (Protocols of the Elders of Zion, Jews control the government/media, etc).
Honestly, that chapter (and indeed the whole book) is absolutely fascinating, so if you can get your hands on the book I'd recommend just reading it, but I'll try to sum up aspects here. But before I do, I'll emphasize something: I'm going to be getting a bunch of stuff out of a book that, as I mentioned, is called Antisemitism in America (though also from other sources). It's therefore going to include a lot of the worst elements of what was going on in the US toward Jews at the time. That said, overall, Jews were lived largely normal lives with freedom of religion and much opportunity (though limited by the social antisemitism mentioned above). In fact, one of my personal pet theories is that religious Judaism in the US in particular had a massive boost specifically in this era when, in 1940, the 40 day work week went into effect, standardizing the two-day weekend, including the Jewish Sabbath. The fact that Jews had a great deal of freedom and excellent quality of life did not mean that they weren't seriously affected by the large amounts of antisemitism in the air in this era, of course.
When WWII began in 1939, the US was by and large against intervention. (This, for the record, included many Jews.) One of the major movements in favor of American isolationism was the America First movement, which had about 850,000 members, mostly in the Midwest, and was a hotbed of antisemitism. It was supported by figures including Henry Ford and Father Charles Coughlin (more on him below) and had members who made comments about how "'Jews were now in possession of our Government' and were causing the 'panic and wars that ruin everybody'" and "insisted that both Franklin and Eleanor Roosevelt were Jewish and so were 90 percent of the New Dealers... that Prime Minister Winston Churchill was half-Jewish, and stated that the English government was a 'Jewish government.'" The final straw was when Charles Lindbergh, who had several years earlier received an award from Hitler, gave a speech in 1941 in which he blamed Jews, among others, for trying to push the US into the war, specifically stating that "their greatest danger to this country lies in their large ownership and influence in our motion pictures, our press, our radio and our Government." To their credit, the nation generally reacted very harshly to this, with even isolationist-minded newspapers and figures condemning the remarks; however, some did note the hypocrisy of criticizing Lindbergh for his remarks while also tacitly accepting the social antisemitism endemic in American society.
Jews were also the targets of hysterical suspicion against minorities, along with African-Americans, Hispanics, and of course Japanese-Americans. Contemporary reports indicate that Jews worried about their safety and felt overt hostility, which is unsurprising considering the results of several opinion polls. In one published in 1945, 58% of respondents felt that Jews were too powerful in the US, up from 36% seven years earlier. (In the meanwhile, Jews were having a terrible time convincing the US government to intervene on behalf of the Jews in Europe, ironically.) In 1939, 13 million Americans polled by Fortune magazine agreed that Jews should be deported "to some new homeland as fast as it can be done without inhumanity." In June 1944, 24% of respondents to another poll identified Jews as the biggest threat to the US, compared to Japanese at 9% and Germans at 7%. In 1942 45% of US high school students polled said they wouldn't want to room with a Jew in college, second only to African Americans (78%) and with the next highest being Chinese and Catholics (9% each). At the same time, 42% of factory workers polled said that they wouldn't want a Jew to move into their neighborhood, second only to African Americans (72%) and just ahead of Chinese (28%). Between 1940 and 1946, the number of people reporting hearing negative talk about Jews in the last six months jumped from 46% to 64%. While Jews didn't face major riots, such as the Detroit Race Riot and Zoot Suit Riots in 1943, they still experienced a great hostility in the surrounding culture.
One of the reasons was the circulation of antisemitic media, often with a Christian bent. Father Charles Coughlin was one of the main offenders. He was a Detroit priest with a widely consumed radio show (with 29 million Americans reportedly listening to his show at least once a month in 1938) and a weekly newspaper, Social Justice, with a circulation of about a million which published 102 antisemitic articles from 1940- April 1942 (a bit less than one article per week, on average). He was essentially shut down by his immediate superiors in the Catholic Church after the US government intervened, judging Coughlin to be especially harmful in wartime, as was done to other figures such as Gerald Winrod (whose magazine had 100,000 subscribers) and William Pelley (who was sentenced to 15 years in prison for impeding the war effort). Some Christian women's groups, particularly those organized by the parent organization "We, the Mothers," also traded in antisemitism. The antisemitism could go from rhetoric to action quite quickly- Irish Catholics (often spurred by antisemitism coming from the pulpit), particularly members of the Christian Front, became known for their harassment of and even attacks on Jews in cities throughout the Northeast and Midwest, with one particular string of attacks on Jews by Irish Catholic gangs in Boston becoming so endemic that it led to an investigation by the governor of Massachusetts, who concluded that this had been happening for some time and was being covered up by the police, leading to the replacement of the police chief. Protestants were often no better- textbooks used in Protestant private schools were found to be riddled with antisemitism, as were speeches by ministers and the attitudes of their parishioners, with at least one whole town essentially ostracizing the few Jewish residents for their supposed war-mongering.
1/2