I didn't say all the people were worked to death. Obviously not. It was just more common. The working conditions in the sugar plantations were much harsher, the growing season was longer, and the deadly diseases (such as malaria) were much more rampant.

Of course there were survivors. Another factor was that U.S. law made the caste system much more strict, whereas in some of the countries in the Caribbean and South America, miscegenation was not illegal or not strictly enforced.

To put it into perspective, in the U.S. in 1860, there were about 4 million enslaved black people and another 500,000 free black people (about half in the North and half in the South). Those 4.5 million black people were the descendants of roughly 400,000 people captured from Africa, almost all of them before 1808 (when Congress made further importation illegal, though there continued to be some law-breaking). That's about a 10-to-1 ratio of imported person to descendant about the time that slavery was outlawed.

In Brazil in 1872, there were about 1.5 million enslaved black people and a further 4 million free black and free mulatto people. Those ~5.5 million black and interracial people were the descendants of the 4 million people captured from Africa and shipped to Brazil. That's substantially less than a 2-to-1 ratio of imported person to descendant.

The reason for the discrepancy? A lot more enslaved black people died in Brazil, and there was more miscegenation.