Wasn't Canada already doing this? Were there any calls for war with Canada over this?
2. The CS attempts to expand southward (Cuba or Central America), Britain says no way are we letting a slave country expand. They form an alliance with the US and war begins.
Are you aware that at this time in history the entire Caribbean and much of Central and South America had the bulk of all slave operations?
I think the US component of the Slave trade comprised something like 3% of the total.
The Atlantic slave trade was ended by Britain in the 1860s.
Britain had freed its slaves in the West Indies in 1834. France freed its slaves in the West Indies in 1848. The Danes did the same in the same year, the Dutch in 1863.
Most of the South American and Central American countries abolished slavery when they became independent or shortly afterwards. Brazil and the remaining Spanish colonies still had slavery, but they were (with the US) the exceptions, not the rule.
So what the heck are you talking about, Diogenes?
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Would there have been another war?
Probably. War over the western territories was possible. So was war over the Border States. There would have been anti-slavery and pro-secession militants active in the border areas. Sooner or later there would have been a clash that would serve as a justification for war.
There also could have been a Confederate war with Spain or Mexico or Central America over the expansion of slavery. Either the US or Britain might have gotten involved in such a war.