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Had the CSA managed to break away, I can't help but think the United States would be inclined towards pursuing some sort of containment policy with regards to the Confederacy.

The CSA is a threat to the Union so long as it has free access to the wider world and thus can serve as a launching pad for foreigners to challenge the United States. Meanwhile the CSA would have a number of routes in which it would seek its own expansion - Vidaurri's Nuevo Leone and Coahuila, Spanish Cuba and Puerto Rico, and perhaps the Dominican Republic (Baez showed he had no issue selling his nation to slavers). Southerners pre-war showed they had an inclination for expansion southwards.

Folks like Hamilton Fish and William H Seward, meanwhile, were ardent expansionists.

The United States, in my view, would likely pursue a post-war equivalent to Scott's Great Snake. Supporting Mexico city against Vidaurri or wooing Vidaurri into being an American friend. Grabbing the DR for itself before the Confederates could get it. Purchasing the Danish West Indies to gain a crucial naval base. Either liberating Cuba and PR or conquering the islands for itself. The CSA would create a geopolitical need for actions that OTL the US needn't take.

Thoughts?
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