I don't see it as that unusual. The extreme pending threat of fascism was readily apparent even before WWII got underway in Europe and China. Still, it took the Pearl Harbor attack to get our nation pulling in the same direction. Up until then, there was a ton of support for Hitler's Germany. In this area and out toward Reading and south toward Lancaster, there was a whole lot of pro-German Bund action, not to mention out-and-out Nazis and KKK. There was papa Kennedy, and Lindberg, and Vandenberg -- all trying to at least keep us from siding with Britain or pushing us to line up with Germany. We also had local communists and militant socialists who went off to fight in Spain and those who strongly opposed this.
The country never came together during the Viet Nam war ( the come together should have been to get the heck out of there), came together briefly after 9/11, but the Iraq invasion ended the unity. We didn't come together for more than about a week after the 2008 near-depression.
We had the first very bloody Civil War and then the second civil war over integration.
We were not a unified nation during the American Revolution.
Decades of labor vs management and the tycoons against the poor, including the last naval battle in territorial U.S. at a steel plant in PA.
Certainly not unified during the gilded age or Roaring Twenties, and both those period had politics limited to only white males in one case and primarily white males in the other.
Partisan politics have been this divided often in our past. We've fought even harder over immigration in the past, on the role of women in politics (none vs just voting).
A largely unified America, which generally pulled together is myth, which became reality during brief periods of time.
Had a close up view of the final death throes of Bethlehem Steel's Bethlehem plant. I think it could have been saved Labor and management could never put aside the pickier bits of their forever battle to save the plant: some capital investment and management-labor cooperation likely would have given at least another decade of good life, but the death match was on.
I think there is more factual uncertainty today, regarding both the Covid and the economy than existed around important facts and projections related to those prior divisions. Also, the Covid hit at a time of near religious/cultural war in our nation, very reminiscent of the strife between the secular model Kemal Ataturk and the Islam-centered model of Erdogan in Turkey over the past quite a few years.