Correct me if I'm wrong, but I thought that the entire point of the confederacy was their claim that they were no longer part of the United States and were, in fact, now a foreign country. You can't declare yourself a different country, then complain that you're treated like one.
The Confederate cause did not include attacking, invading the North or antagonizing the North in other ways.
Yeah, shelling Fort Sumter wasn't the least bit antagonizing to the United States.
Sumter gets all the attention but there were many more federal institutions attacked and seized:
Alabama seizures:
United States Arsenal at Mount Vernon
Fort Morgan
Fort Gaines
Arkansas seizures:
United States Arsenal at Little Rock
United States ordnance stores at Napoleon
United States subsistence stores at Pine Bluff
Fort Smith
Florida seizures:
United States Arsenal at Apalachicola
Fort Marion
Barrancas Barracks
Fort Barrancas
Fort McRee
Pensacola Navy Yard (Warrington Ship Yard)
Georgia seizures:
Fort Pulaski
United States Arsenal at Augusta
Oglethorpe Barracks
Fort Jackson
Dahlonega Mint
Louisiana seizures:
United States Arsenal at Baton Rouge
Baton Rouge Barrack
Fort Jackson
Fort Saint Philip
Fort Pike
Fort Macomb
United States paymaster’s office at New Orleans
New Orleans Mint
Mississippi seizure:
Fort Massachusetts on Ship Island
Missouri seizures:
United States Arsenal at Liberty
United States ordnance stores at Kansas City
North Carolina seizures:
Fort Johnston
Fort Caswell
Fort Macon
United States Arsenal at Fayetteville
Charlotte Mint
Texas seizures:
United States Arsenal at San Antonio
San Antonio Barracks
Camp Verde
Fort Clark