Perhaps my choice of the term "direct" is overly specific, but I feel like this is a very nit-picky quibble. The underlying point I was trying to make doesn't change, which is that the United States benefited hugely (in purely economic terms) from slavery. Whether or not we would have been as, less, or more successful without it, or whether it has been helpful to others, is an orthogonal discussion. As I said, I am not making the claim, and never intended to, that slavery was the only cause of American prosperity. If this is the primary dispute you have with what I said, I readily accept the correction and we can move on.

However, if your intention is to dispute the claim that slavery was immensely beneficial to the development of the American economy, or to suggest that the morality of American slavery was somehow mitigated by other historical examples of slavery, I strongly disagree. I think in general this mentality is incredibly disrespectful. Acknowledging the role played in our success by the (unwilling) sacrifice made by millions of slaves and Native Americans is the very least that we can do.