Slavery in the Americas was a uniquely horrible institution, for reasons I do not even pretend to understand. But the start of it is easy enough to grasp, at least in rough outline: Europeans say "Hey, this would be a great place to grow sugar cane!" They learn the locals don't want to work for them, so then force the locals to work for them, and wipe them out with both disease and insanely brutal treatment. Import slaves from Africa, rinse and repeat.
Now let's suppose these people do things very slightly differently. In modern and very casual vernacular:
"We need workers but the locals won't do it. So where do we find workers?"
"How about Africa? Lots of the people there, we can bring them over."
"That's going to be expensive."
"Well, yes. But we can recoup that by using indentures. Bring them over, get their work for room and board and medical care for, let's say, ten years."
*sound of chalk on board*
"That works. Free workers are more productive than slave workers, and if don't treat them too badly, we won't need to replace them so often."
"Let's do this." And they do.
So, the Caribbean plantations have paid workers instead of slaves. They're treated normally, by the standards of the time, rather than beaten and work and starved into very early graves. How does this change the course of history in the Americas?