Final answer:
James Loewen has noted improvements in the depiction of the Civil Rights Movement and the relationship with Native American people in newer American history textbooks.
Step-by-step explanation:
Historian James Loewen has been critical about the representation of historical events in American textbooks. In particular, he believed that newer editions of textbooks have shown improvement in chapters exploring America's relationship with and mistreatment of Native American people. These revisions are said to have improved the accuracy of the descriptions, removed historical myths, and used more authentic language. Additionally, information about the Civil Rights Movement, including the contributions of Black women to the Suffrage and Civil Rights movements, as well as the struggle for LGBTQ rights, has been improved in terms of detail and historical accuracy.
Thus, based on the information provided, the topic that Loewen believed to have been improved in American textbooks is the Civil Rights Movement (D).