In the ACW, more than 600,000 men died during four years, and even today, some people have grudges over it.
Roughly at this time, Europe only had four comparably minor wars: The Sardianian-French-Austrian war 1859, the German-Danish war 1864, the Prussian-German war 1866 and the Franco-German war 1870/71.
Why this big difference? Both North America and Europe were part of the western world, their technology levels were comparable... so why?