While I'm not qualified to speak on the US Civil War, I'd say that there isn't much perception in contemporary sources that Infantry advances and Cavalry charges in the latter part of the Napoleonic wars were in any way useless. Indeed, well-timed charges and countercharges decided several key points of Ligny, Quatres-Bras, and Waterloo, the last battles of the Napoleonic Wars.
When we think of the Infantry 'charge', though, we need to remember that the modern image of two formations smashing into each other and fighting it out with bayonets was not only a rare occurrence but also not the desired outcome of any charge. Infantry charges are best imagined as a game of chicken; neither side particularly wanted to go into close combat without any armour and no weapons except usually cheap and poorly-forged bayonets. If the attackers could weather defending fire with good discipline and advance as one, defenders would usually retreat rather than face close combat. If, on the other hand, the defenders delivered disciplined fire and stood their ground, charges would usually waver, with that initial hesitation compounded by successive volleys until the attackers reeled back and either reformed or routed. The goal of a charge was generally to push the enemy out of their position and hopefully break their discipline - and a charge did not need to connect to do this.
This is not to say that infantry-on-infantry close combat did not happen, but it generally happened in a context of either highly disciplined or motivated troops (such as Swiss troops defending the Grande Armée's crossing of the Berezina from Russian assault) or fighting in urban areas (such as the fighting in Ligny or Plancenoit during the Waterloo campaign).
(It's worth noting at this juncture that the image of French columns inexorably rolling towards enemy lines in order to break through them like battering rams is, by and large, a persistent myth. French doctrine was to deploy from a column of companies (really more of a boxy rectangle shape) into line to deliver an assault; sometimes this failed due to the nature of the ground and the enemy being closer than the French anticipated. This was particularly common when facing the British Army under Wellington, whose heavy use of skirmishers and deployment on reverse slopes, when combined with the relative inexperience of most French troops facing him, led to some French commanders faced with the choice of trying to win a firefight in column or pushing on to try a charge.)
Cavalry charges were also highly effective in the late Napoleonic period; while Ney's advance at Waterloo was ineffective, the earlier charge by the British heavy cavalry against d'Erlon's corps on the other side of the Mont-Saint-Jean ridge was highly effective, and only tarnished by the poor discipline of the British leading to their rout by other French troops. While Cavalry were ineffectual against infantry that managed to form proper defensive formations, they were lethal against infantry or artillery caught in the open. Skirmishers, no matter how well-trained, were effectively helpless against cavalry that surprised them, owing to the diffused nature of skirmish lines. Infantry in line were generally unable to drive cavalry off with firepower alone, and if cavalry attacked from the side of a line there was little an infantry battalion could do to save itself from rout. Finally, charges were absolutely vital in driving off enemy cavalry, and it was at this that French cuirassiers excelled; unlike infantry charges, cavalry-on-cavalry charges often resulted in sword-to-sword fighting, and the front-and-back cuirasses and helmets of French cuirassiers gave them a significant advantage in this area.
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