North America's use of slavery was relatively low compared to many other places in the world. Even within the United States itself it's interesting to compare the states where slaves disproportionately ended up to those where they did not. And the Confederate/Union states works as a pretty solid proxy there.
- Confederate: South Carolina, Mississippi, Florida, Alabama, Georgia, Louisiana, and Texas
- Union: California, Illinois, Massachusetts, Michigan, New York, Ohio, Pennsylvania, and many others.
Suffice to say, slavery does not seem have had a lasting positive effect for the states that most actively utilized it. Ultimately I think the reason slavery is more of a focus for the United States than other countries is not because of any unusual usage of slavery, but because of an extremely unusual outcome.
For instance Brazil alone ended up taking on about 5 million slaves yet, like much of the south, has little to show for it. The point of this is not to say 'what about other countries' but to emphasize that the relative impact of slavery in the US was smaller than in many other places, yet we achieved vastly more than those places. So to attribute the exceptionalism of the United States to slavery, in any meaningful way, seems driven more by bias than logic.