The most lasting impact is that the sheer number of deaths of the best of the European male population on all sides, ultimately led to the feminization of Western society, which is why in large part where are where we are today.
Losing about 4% of their population in the First World War didn't make countries feminized enough to avoid the Second World War. Nor did losses in our Civil War make Americans more feminized. So I'm going to have to put the blame or responsibility on non-biological, non-genetic factors.