Wrong flag.
I’m actually impressed as how “not Confederate” Fort Sumter was, and how striking for the war to start there. It is literally an artificial island built & occupied by the US military. All the other forts were on legitimately Confederacy-governed land, and were duly abandoned. Sumter was as clearly Northern-owned as could be. I contend that the Southern assault thereon constituted (if arguably subject to legitimate arbitration) an attack on a foreign country, which justifiably pushed back until the offending party relented, returning Fort Sumter and (oddly) all lands associated therewith.
By my pet theory, the entire war could have been avoided by letting the North keep the military island they literally built. This also expresses US axioms: we recover our own, people & property, at all costs - it’s something that differentiates us from most other cultures.