True enough. The last few months of the war saw both the Army of Northern Virginia and the Army of the Potomac locked in the same static trench warfare that Europe would see 50 years later.
European observers dismissed the lessons as the result of amateurs playing war and ignored the effects of rifled muskets and concentrated artillery on mass lines of troops marching across an open field. They still thought that Napoleonic warfare was viable, and would go on thinking that till they bled Europe white.
Of course, there were more than a few Union and Confederate generals who were still enamored of Napoleon themselves, including Lee, who blew the war at Gettysburg by ordering Pickett's Charge, a hopeless attempt to break the Union center. He told Longstreet that by breaking the center, he'd crush the Yankees like Napoleon had done at Austerlitz. All he managed to accomplish was waste a lot of his troops lives for nothing, something the British, French, and German generals would prove themselves more than adept at 50 years later.
Good points. Lee was a great believer in trench warfare and used trenching to great effect. He was called the "king of spades" by his own troops.