I've been reading William Bernstein's A Splendid Exchange: How Trade Shaped the Word, and though just about every page has a part worth blogging about, I found this part explaining black Americans' relative lack of African culture compared to blacks in the Caribbean and Brazil:
Death on the plantation was sugar's constant companion, and those colonies that relied most heavily on cane had the most trouble maintaining their slave populations. The black population of British North America, which grew little cane, increased nearly as fast as the white population. The one exception to the pattern of lower mortality among slaves in North America was found in the southernmost parishes of Louisiana, one of the few places on the continent that grew cane. Conversely, one exception to the high mortality among slaves in Brazil was found in the province of Minas Gerais, which was more dependent on "easier" labor: coffee and dairy production.
The deadly face of "sugar demographics" is easily seen today in the cultural differences between the black population in the United States and Canada and that in the rest of the hemisphere. British North America, because of its vigorous population growth, required ever-smaller infusions of African slaves. After 1800, the relatively high fertility and low death rates among slaves in the United States meant that southern plantation owners simply did not need to import more Africans. The American prohibition of the slave trade in 1808 easily passed trhough the southern-dominated Congress for just this reason: the Americans' abolition of the slave trade crippled their Caribbean and Brazilian competitors. By 1808, almost all North American slaves were native-born, and by the Civil War, relatively little culture member of Africa remained. The Caribbean islands and Brazil, on the other hand, required a constant flow of Africans; well into the twentieth century, the Yoruba language flourished in Cuba, the last bastion of the New World plantation society, and African influences still pervade Caribbean culture.