I'll leave it to the historians on the board, but I'm pretty sure slavery is well covered now as is Vietnam. The War of 1812, probably not so much; and the "violence Columbus was responsible for," I'll plead total ignorance to.
no it is not - I've been responsible for teaching history by the textbook and the textbook has been found wanting.
I've been on curriculum panels and revisionist curriculum panels and review boards for textbooks in addition to teaching history and literature.
I'm not sure when the last time was you picked up a mainstream American history textbook, but we just adopted new ones 3 years ago - and all of the sections I mentioned above, as well as scores of others, leave a great deal unsaid