So I'm a huge history nerd, And I was under the impression that the atomic bomb did not force Japan's surrender. Instead the primary factor was the Soviet Union declaring war on Japan and threatening to invade Hokkaido.
However, whenever I bring this up in public, I'm met with fierce resistance. People argue with me to the teeth over this, despite there being quite a bit of literature that suggests the contrary.
I think this is odd because most people have no problem accepting that what we were taught in normal history books might be biased or wrong.
Example: history books say that Americans settled the West, but most people nowadays assume that it was actually an invasion.
We were taught that the atomic bomb forced Japan's surrender in history books. So why do people not question this?
Is there actually a debate among historians? Or is resistance to The idea that the Soviets forced Japan surrender simply a matter of being uninformed?
Most current popular knowledge in the United States about the atomic bombings of Hiroshima and Nagasaki is centered exclusively around the terms of the historical debates that were taking place around 1995, the 50th anniversary of the bombings, when it became a locus for a "culture war" conflict (like "Critical Race Theory" today and a lot of other things). This was politics by other means, and the understanding of the bombings became core to a debate about the history and present identity of the United States. The most prominent location of this conflict was the Smithsonian's Enola Gay exhibit fracas, but one sees the ramifications of this throughout lots of books and debates that came out in that era, both promoting the "orthodox" view of the "decision to use the bomb," and the "revisionist" view (that framed things in basically the same terms, except it argued that the bombs weren't necessary and that the US dropped them to try to intimidate the USSR).
That particular white-hot moment made such an impression on several generations of educators, popularizers, and journalists that it is incredibly, incredibly hard to make them see it in any other terms. The historical debate has shifted quite dramatically since then, towards many other things (including the essential consensus that there was no "decision to use the bomb" and the entire terms of the previous argument are anachronistic), including the question of the role of the Soviet invasion versus the atomic bombs in Japan's eventual agreement to surrender.
But there is a deep cultural lag in the United States, reflected in textbooks, news media, documentaries, popular books, and the like. So yes, it is entirely unsurprising that most people have not heard of this particular debate at all and still find it surprising even though in its modern form it is 20 years old, and earlier versions of it existed in the 1940s and 1950s.
But to your point as to why people hold such strong views on a topic that they themselves would probably, if pushed, admit that they only have a cursory understanding of — it is because this is one of those topics that is not seen as a merely academic question (like "how were medieval samurai swords actually made?"), but as one that points to fundamental understanding of the identity of the United States. This is true of both the 1990s "orthodox" view (United States essentially good) and the 1990s "revisionist" view (essentially bad), and the question of, "what actually did the Japanese think and do?" is almost irrelevant to most people when it comes to that approach to it (and just complicates things immensely). So I would say it is more than just being not informed, but it is one of the many places where historical narratives are subscribed to as part of broader political identities, and so are much harder to dislodge. (Other places where one sees this are discussions about the Civil War, the history of slavery, and — less so today than 20 years ago — McCarthyism.)