Actually it was the Brits who, in the beginning, set the standards and called the shots on slavery in the colonies.
The north won the war so they got to write the history.
And the losers got to write the myths.
And so did the winners. Much of what the public believes about the Civil War is in fact a "Winner" created Myth. Nobody's heard of the Corwin Amendment, and nobody knows that Lincoln had sent a war fleet to Charleston with orders to attack the Confederates.
Yes. The Brits and others brought them to the USA but the north had more than their share. They got the moral high ground when they realized they preferred cheap European labor. They didn’t have to house and feed the European families.
Slavery has a horrible history. It is sad it was ever allowed in the USA.
But I don’t believe most southerners sent their children off to war so wealthy landowners could own slaves. I certainly wouldn’t have gone to war for that. There’s no myth about that.