Not sure what that is supposed to indicate? USA was a big place, even then. Most northern states had abolished slavery even before Britain, France, and especially Spain did. Maybe we should have a quick refresher on European values?
> The article talks about European colonies, so would these have been European values then since America did not yet exist?
Slavery is an expression of capitalist values.
Frederick Douglass is Karl Marx's ideological predecessor.
You aren't wrong that the European powers were slavers. That being said, the culture of the 13 American colonies is the first appearance of the unique Euro-American culture that dominates the United States.
It's wrongheaded to deny the central importance of slavery to American culture and values.
In the United States, the land of the small business owner, slaves mixed socially and sexually with their captors and with the culture of their captors.
For this reason, the culture of the United States is deeply affected by the institution of slavery in ways that are alien to the European powers.