For a more objective judgment, I would suggest to look at the wars that were fought in Europe, or by European armies, around the same time:
the Crimean War of 1853–1856
the Wars of the Italian and German Unification
the French-German War of 1870-1871
These conflicts, IMHO, make the Union Army at the end of the Civil War look quite good by comparison.
It had vey modern small arms, like breech-loading and repeating rifles, revolvers, and the Gatling gun. Its artillery was fully adequate, though not outstanding. Krupp's breechloading cast-steel guns with their percussion-fuzed shells would prove revolutionary, and a real war-winner in 1870. Though it may be said, that the British Whitworth rifled breech-loader, used in small numbers during the Civil War, pointed the way for Krupp.
US cavalty was probably the most modern of its era, having done away with lancers and cuirassiers in their increasingly useless breastplates. With their revolvers and Spencer carbines, they had superior firepower, while European cavalry was still supposed to win battles through massed attacks with sabers. By 1871, it had become clear that such tactics were increasingly suicidal.
In terms of leadership, lots of political generals and inept professionals had to be winnowed out during the first years. But by the end of the war, Sheridan, Grant, and Sherman had fully proven themselves. They knew how to conduct strategy campaigns on several theaters of operations, had experience in amphibious warfare, campaigns, use trains for troop movements and telegraphs for command.
The European equivalent of political generals were monarchs taking command of their troops, like Franz Josef of Austria, or Napoleon III. The results were usually comparable - they both lost to the professionals on the enemy side.