To a certain extent, the answer to your question lies in your question itself. That is, there is no one curriculum to speak of so it's less about changing curriculum and more about the philosophies and mindsets of adults in and around school.

Due to the 10th Amendment, education is a matter left up to the states. In a practical sense, there is no national system for determining learning standards, curriculum, pedagogical practices, textbooks, or assessments. However, there is a phenomenon known as the "grammar of schooling." Coined by two educational historians, Tyack and Cuban in the late 1990s, the "grammar" is the stuff that mark American schools as being American schools, despite the lack of any policy that mandates those things. It includes the things around the learning like apple motifs, afterschool sports and clubs, calling teachers by a gender moniker and their last name, dress codes, soft gender segregation, etc. As well as the stuff that is explicitly about learning - which includes curriculum.

First, some quick modern day context. Lalor (2017) describes curriculum as having a variety of layers. There's the:

• written/formal curriculum - what's in the textbooks, state learning standards, and written down by adults (sometimes called "scope and sequence.")
• taught curriculum - what's delivered in the classroom (knowledge, skills, and dispositions)
• assessed curriculum - what's evaluated through formal measures
• learned curriculum - what students actually learn as a result of being in school

John Oliver's recent piece (which we talked a bit about in a recent FFFA) dealt with a combination of these. In effect, he said people are learning "bad" history due to poorly written textbooks, limited professional development for teachers, and more.

His analysis helps us see how, when we talk about history curriculum in American schools, we're dealing with a whole bunch of different variables depending on where in the country we're talking about. In this piece, I go into the differences in the history curriculum between New York State and Texas here, which speaks to differences in the written and assessed curriculum.

In this piece, I go further into the matter of textbooks, which is one of the ways various adults have tried to change the formal curriculum, with the hope of changing the taught and learned curriculum. In 20 years, we can get into the history of national standards like the Common Core and their role in shifting standards.

Happy to answer follow up questions about the linked posts!