Other countries, by and large, already either had centralized systems or didn't have climates suitable for plantation farming in the first place. It's useless to speculate about how slavery and the later oppression of black people could have ended in America: if Southern whites were willing to fight and die to preserve the institution, they certainly weren't on the fringe of abolishing what was essentially the cornerstone of their entire culture and economy for "moral reasons". It's easy to abolish slavery when there's no good rationale for it; even in the North, abolitionists with genuine concern for black people were a minority compared to people who just thought it was bad economics or who felt that concentrated wealth in the hands of slaveowners had the potential of reducing economic opportunities for free white farmers.[1] Since you're so fond of comparing things to Iraq, an interesting analogy is to think about how much you hear people complain about the number of American casualties in Iraq, or the cost of the war and its impact on the federal debt and deficit, and compare that to the small number of bleeding heart liberals complaining that it was bad for the Iraqis. How many times were dead US troops a talking point compared to dead Iraqi civilians? This isn't a criticism, but a point of illustration--just as white Americans today don't care about Iraqis, white Americans in the 19th century didn't care about black slaves.
The fact is, "states rights", and the whole idealization of the pre-Civil War system in America, is a broken and evil ideology that was used as an indirect defense of slavery in the 19th century and segregation and disenfranchisement in the 20th. What you are really saying is that you value that system of government so much that you would prefer to let people continue to be enslaved until such time as their enslavers felt so inclined as to free them out of their own moral goodness. And I would like to know why.
[1] This is an interesting precursor to contemporary complaints about big business, for instance Wal-Mart. Today, people complain that Wal-Mart is a huge company that puts local businesses out of business. In the 19th century, people complained that plantation slaveowners were rich people who put small-time family farms out of business, especially if slavery were legal in the expanded western territories. Legalized slavery would allow slaveowners to expand their operations and use their stock of slaves to farm a lot of land at scale, leaving nothing left for the white settler who wanted to go build his own farm in the west.
The fact is, "states rights", and the whole idealization of the pre-Civil War system in America, is a broken and evil ideology that was used as an indirect defense of slavery in the 19th century and segregation and disenfranchisement in the 20th. What you are really saying is that you value that system of government so much that you would prefer to let people continue to be enslaved until such time as their enslavers felt so inclined as to free them out of their own moral goodness. And I would like to know why.
[1] This is an interesting precursor to contemporary complaints about big business, for instance Wal-Mart. Today, people complain that Wal-Mart is a huge company that puts local businesses out of business. In the 19th century, people complained that plantation slaveowners were rich people who put small-time family farms out of business, especially if slavery were legal in the expanded western territories. Legalized slavery would allow slaveowners to expand their operations and use their stock of slaves to farm a lot of land at scale, leaving nothing left for the white settler who wanted to go build his own farm in the west.