While the loss of New Orleans was a blow to the Confederacy, both psychologically and materially, I doubt it lost the Confederacy the war. Fact is, the Union blockade of the MS River had already turned New Orleans into something of an economic ghost town. The blockade of the MS River, and thus New Orleans, may have been decisive in that it stopped the Confederacy from exporting the cotton needed to pay for war supplies, but that blockade occurred in 1861 and was in any case inevitable.