Being a nation of ideals is difficult. Not everyone is going to share those ideals and that sometimes causes conflict. I have a personal ideal not to kick dogs, unfortunately most dogs do not understand or share that ideal. If the dog charges me I am going to kick the shit out of it in self defense. It is not a failure of my ideal, but a failure of the dog to understand that I don't want to kick it.
Perhaps part of the problem you are having reconciling American history stems from some of the misinformation you have posted above. Is this what they are teaching at Foothill College in Ca.? Perhaps the misinformation comes from..
If it is Foothills I will be happy to write to the history department and inquire why they have decided to teach history that is not supported by ... history. Those other nations I cannot do much about, anyone I contaminated with my "liberal", "capitalist", "infidel" ideas would be censured, arrested, or worse.
I accept that the American Government is flawed, We remain in a constant state of civil war over interpretation and implementation of the Constitution. We just do it without killing each other. We are having our next conflict November 2 this year. Bring your ink pen it is the only weapon allowed.