Lincoln knew that given enough battles with equal or even higher Union losses the Union would still win the war. He called this: "the terrible arithmetic". The Confederate white population was less than 6 million. There were 22 million in the North. There was never really any doubt which side would win the war if the Union remained determined to keep fighting.
Taken as a whole, actual combat deaths for either side cannot be compared to the much greater death toll attributed to disease etc. But in combat causalities, the North suffered many more than the South.
The NRA of today was birthed in 1871 as a direct response to faults which arose during the civil war. In that war, as a whole, the superior marksmanship of the average Confederate troops (more rural) was far superior to those of the Union Army. (more urban)
In battles of the western campaigns, the rural western army troops of both sides were much more evenly matched as to having a lifelong familiarity with firearms and being accurate with same, and the causality ratios reflected this.
The NRA’s purpose was to correct that acknowledged accuracy imbalance of the civil war, to encourage and teach marksmanship for all American civilians, especially the young.
http://www.nrahq.org/history.asp