If you had a chance to read /u/Kugelfang52's really interesting answer, you likely noticed that one thing we can be sure about textbook creators' is they have zero interest in being objective. So, while they don't exactly pick a stance, it's safe to say they - and they may or may not be a historian - approach history with an eye towards a particular narrative. I've written about textbooks before and I'm going to pull from some of them to provide more context. Granted, my answers are American-centric so those who are familiar with non-American textbooks might have more to offer on how it works in different countries.

The first thing to speak to is that American public schools, through a process of cultural norming that came about through deliberate and indirect actions by adults have adopted a number of recognizable features that indicate that a particular place is a school. One of those features is something referred to as Americana. Examples include things like saying the pledge, treating Christopher Columbus as a hero, George Washington and his cherry tree, Lincoln and his log cabin, etc. While on one hand, these can feel like ways of encouraging patriotism and simplifying history for younger learners. On the other, it's not about teaching an accurate history, it's about supporting a narrative that's been shaped by whiteness, Protestanism, racism, sexism, ableism, and more.

What this looks like in practice is that in many mainstream textbooks (more on the history of the textbook industry in my answer to the question, Who decides what goes in a history textbook?) would set aside "influential women" or "notable Black Americans" in textboxes, indicating to the student that there's history and then there's the things women did in the past. In contrast, independently developed textbooks, like the one that Dr. Carter G. Woodson developed while he was a teacher at Dunbar High School centered Black Americans in the history of the country. (You can read more about his rationale in his 1933 book, The Mis-Education of the Negro.)

The degree to which whiteness, Protestanism, etc. manifest themselves differently in textbooks varies wildly across the country. From that linked answer:

In effect, by the 1940's, textbook publishers had three groups of consumers.

1. states that adopted textbooks - and helped districts pay for them
2. states that told districts what textbooks to adopt and expected districts to pay
3. states that let districts select which textbooks to use

In terms of your question, this means that the people purchasing textbooks in each group have different motivations. Which means those writing the textbooks have to attend to different things when creating a textbook. Those in group 1 and 2, most notably Texas, look for something that will work for every school in the state. Usually, this means they look for textbooks that reinforce a state identity. (More on that in this response comparing history education in Texas versus New York State.)

Those in group 3 are more likely to have history standards linked to local history, which they're going to be looking for textbooks that provide a general overview and work to supplement the textbooks with other readings. So textbook authors will focus on providing a general American history. And again, when it comes to the nature of that history, it's shaped by what districts ask for, which shapes how editors structure the textbooks, and so forth and so forth.

You may be interested in an answer I wrote here. In it I address the opposition of segregationist Texans to the UN Declaration of Human Rights due to its challenge to racial hierarchies. It sheds light into the power that educational bureaucracies play in shaping textbook narratives.