And before each post, could the challengers type in a regional name that cooresponds to the CSA? If the USA is America, and the Confedaracy is considered not American, the Confederacy is _____ (Confederra?).
What?! Technically there are Americans living in Colombia, El Salvador and Argentina, but we just call them Colombians, Salvadorans and Argentinians. The Confederacy is American since it was formed out the United States, the citizens are Americans, as in 'Confederate States of...'. Getting even more technical, they wouldn't be Confederates - per say - but Virginians, Flordians, etc.
Since I don't quite get the gist of your entire challenge I'll just disregard it. The likely OTL sites for Treaty Ports would be Providence, Boston, Martha Vineyard, Charleston, Savannah, Mobile, Galveston, San Diego, Astoria, Annapolis or Baltimore, Richmond or Alameda, CA. and Bainbridge Island, WA.
I purposefully did not choose New York, New Orleans, San Francisco, since I figure that those ports would still be vital ports, just excluding foreigners - much like the historical treaty ports in China and Japan. However, its likely that an OTL city nearby by may be a treaty port, like Brooklyn or Staten Island. Islands may be a good port, as we have seen with Hong Kong.