We must never repeat these mistakes of the past.
The United States has a proud history that is rooted in the notion that it is exceptional and on higher moral standing than many of its global peers. While this is true in many respects, it is also undeniable that America, just like any nation, has also erred greatly at times throughout its history, occasionally with deadly consequences. Americans have plenty to be proud of, but they must also be keen students of their own history and learn from their mistakes, or else they will be doomed to repeat them.
There are many triumphant moments in American history, but there are also some truly dark ones that we cannot ever repeat.