I counted only wars that more or less fit the original author's criteria, ones that were, or could have been, "caused" by the plague of nationalism in Europe leading to a war between two or more nationalistic European states.
Wars by submerged nationalities against the Ottoman Empire, a non-nationalistic (and mostly non-European) state for most of this period, didn't seem to fit.
Civil wars, such as in Spain, don't fit the criteria either.
Neither did wars of conquest by Russia against tribes in Caucasia or Central Asia or various revolts against Austria, Russia, etc. These wars weren't caused by nationalistic excesses between conflicting European nation-states. Although some of those revolting (Hungarians, Poles) wanted to get their own nation-states so they could themselves engage in nationalistic enterprises.
FWIW, for most of this period Russia was itself a pre-nationalistic state.
As far as the Balkans being primarily non-European, the Greeks, Serbs, Croats, Albanians and others who live there would certainly dispute you on that!
The only way you can arrive at Europe having only 8 wars in the 19th century is if you count Southern and Eastern European countries as being not quite European!
Almost forgot, France v. Mexico!!!! That's the one behind "Cinco de Mayo".