(Thanksgiving, viewed from this side of the Atlantic, is an alien festival.  I know nothing of it apart from what I can glean from films and television programmes.  Those [perhaps unreliable] sources leave me wondering why Americans put themselves through what seems to be an entirely grisly occasion.)

It's true that powerful nations have dark pasts -- that's how they become powerful.  It may be that the Sublime Republic of San Marino has a more or less blameless past.  It isn't true that the British invented slavery -- Britain was a nation from which the Romans took slaves long before it turned to enslaving others.  It is true that the British invented concentration camps.  Curiously the people the British put into the camps were Boers, those fun loving people whose descendants came up with Apartheid (I'm not saying that makes it right).  Perhaps the worst aspect of all this is that the heirs of the people responsible for the dark deeds are the ones who now have power and wealth.  The chances are that, if you're descended from British people who made real money from the slave trade, you're enjoying the wealth they left to their posterity.  If you're descended from ordinary people who never did anything outrageously wrong, you are probably without substantial wealth or influence.  The world is a wicked place.