Well, there is more to know than that, and I found it out much later.

I found out that General Grant, who had fought with credit as a lieutenant in the Mexican War, briefly summarized it as "iniquitous." I gradually, through my reading as a man, learned the truth about the Mexican War which had not been taught me as a boy--that in that war we bullied a weaker power, that we made her our victim, that the whole discreditable business had the extension of slavery at the bottom of it, and that more Americans were against it than had been against the War of 1812.

But how many Americans ever learn these things?
Do not most of them, upon leaving school, leave history also behind them, and become farmers, or merchants, or plumbers, or firemen, or carpenters, or whatever, and read little but the morning paper for the rest of their lives?
The blackest page in our history would take a long while to read.

Not a word of it did I ever see in my school textbooks.

They were written on the plan that America could do no wrong.