what does this quote mean? "Most Americans see slavery as an artifact of the distant past that has no bearing on the nation's present.

What it means:

Most Americans see slavery as an old practice that was completely left behind many years ago, and therefore doesn't affect the way that the US is now.

(But just so you know, most americans don't think that. Only the uneducated do.)

It means that we don't see it as having any affect on us in the present.