[Thunderhawk]

The Civil War could probably have been averted, though the non-slavery-related tensions between North and South would have had to be resolved in other ways.

If slavery never existed, would plantations have come about? Share cropping and paid labour (or even cooleys and peonage) are alternatives to work the fields, but those people are not property. That non-property status means less value is tied in the people, and that in turn means money is available to be spent elsewhere. Large(r) industrialization might have occurred in the South and combined with plantation/farm jobs available due to no slaves, the south may have received a lot of immigration. If either agriculture jobs or industrial jobs attracted immigration, the development of the South culturally and industrially would have been different, and the benefits of centralization may have been something they wanted.

Does anyone seriously believe that if Orientals had been less organized and advanced as societies, and more physically suited for the harsh treatment of transportation across an open ocean and a life of hard manual labor, that they would not have been snatched up in an instant?

Coolies.
http://en.wikipedia.org/wiki/Coolie