The causes and effects of the Second World War are adequately covered in most American History classes. World War II is a popular subject in schools, and it is usually welcome by students. Although it is a big topic, teachers are well trained and they have a good idea of how to introduce the war to students.
In my opinion the current state of history taught in America is not very good. Generally speaking everything taught is only taught from one side and it never looks into the quirks of what actually happened. The history that was taught to me in classes was centered more to create good citizens than to create smart citizens.
Pop culture and education, especially pre-University education, have become inexplicably intertwined in the past few decades, meaning that the brief study of World War II in high schools - if it is ever reached - is based off of a narrative that is hastily written and not particularly true to the complex reality of the situation.
I do not believe the causes and effects of World War II are adequately covered in American history classes. For the most part, history classes in America try to cover everything and you only end up getting a short summary for each major event in the past. When the class follows a linear time line, you may miss out on recent events as well.
No, I do not think that the causes and effects of World War II are adequately covered in American history classes, because most American history classes overlook the economic issues that crippled the Weimar republic in the lead up to World War II. There is also the issue of the United States' lack of immigration visas for Jews that contributed. Neither of these things are covered in history class.