Do you think countries try to "hide" their own actions?

So today in my Holocaust Remembrance class, we talked about how it is against the law in Germany to deny the event.

Fast forward to my American history class.

I opened the text book and there was only one sentence about how Andrew Jackson treated the Native Americans. When I went to the beginning of the book to look at the Civil War section, it didn't mention slavery as being a part of the War at all. Living in Georgia, which obviously is in the South, nobody has ever talked about these events at least in my school.

Do you think countries try to "hide" their past?