As a former school board member (over 10+ years ago now) that has reviewed textbooks in the last 10-20 year span of time, firstly I will say, at least in Virginia, many of the things people are saying either aren’t known or aren’t taught are actually taught and in the textbooks. I would agree that they probably aren’t well known, because I think normal human retention of history taught in K-12 is low, with a lot of people just remembering enough to pass each unit’s test and move on to the next thing, forgetting it by the next school year let alone ten years after graduation.
In my experience it would be unusual for a school system to teach as much about the Bourbons and the Habsburgs. There is typically a decent focus on the reign of Elizabeth I (the final Tudor monarch) in both history and English courses–English classes actually teach a lot of English history in the United States. This may seem strange, but it is often done in the context of understanding our evolution of language. For this reason it is very common for American English textbooks to discuss the Norman conquest because of how it affects the linguistic history of the English language, and to then discuss things like the vowel shift, Middle English, Chaucer, then early modern English the Elizabethan era is discussed because it is the time of Shakespeare who is usually a major unit of study at multiple steps throughout a typical K-12 education.
Now, what I will say is it is not to my knowledge common to present pre-colonial English/British history as part of “American history.” However, it is common for some of it to seep into American-history focused courses.
In Virginia when I was involved in education we had learning standards for:
- American history up to 1865
- American history from 1865 to Present (this functionally often covers only up through the 1980s or so)
- Virginia History
- U.S. Government & Virginia Government
In American history up to 1865, there was an expectation students learn at least somewhat about pre-Columbian history (which was a change from when I was a student), which meant several units on what we know about pre-contact Native American civilizations. There would then typically be units on colonial America, which usually cover at least some degree of English history “as it overlaps”, this will include specific historical or political developments in England/Great Britain that had an impact on colonization.
In Virginia history, as one of the original thirteen colonies, there is a focus on Native American tribes in the area of the modern day Commonwealth, probably even a little more focus on reasons for English colonization and some of the profit-seeking motives of the early exploration “companies” behind early Virginia settlement.
In U.S. Government & Virginia Government, there is a good amount of coverage of things like the English Bill of Rights, John Locke, probably a brief mention of Magna Carta, the conception of the common law legal system etc.
World History to 1500, another standard in Virginia, mostly does not cover much English history for a number of reasons–I believe in the past it did more so.
Overall while I think it is correct to say at least in Virginia we don’t teach English history as “American history”, the history of England has bleed over in the English curriculum, civics/government curriculum, the early American history curriculum, and also probably for any State that was originally a colony, the State history curriculum. While I cannot speak for all fifty states, I believe most have an entire year devoted to the history of the local State.