Actually, the Civil War never really "turned around". Outside the Washington-Richmond corridor, the Union was basically successful.
But the coverage of the war where it mattered (i.e. at the time, the Northeast) focused on the inept performance of the Army of the Potomac around the DC and Richmond environs...hence, a "debacle", a bloody stalemate with no end, an unpopular war with unpopular aims, portrayed by a media pushing their own agenda...
...actually, it's a very apropos analogy.