The image (from here) shows genetic diversity of Europeans summarised in two axes. It is obvious that genetic variation mirrors geography within Europe, but at the same time there is no obvious distinction between countries.
Another way to think about it is that the variation within a country is comparable to variation between countries.
Similarly, clusters of points (genetic groups) are visible from within countries. So the 'race' attribute provides no obvious information on genetic similarities or differences.
Nevertheless, long range patterns are obvious. That is why the overall groups are similar to the geographically defined countries of Europe.
The study is already 2 years old. I find the image to be a strong example of the power of modern molecular genetics.
The image is so information dense that every time I look at it, I find something new to think about. For example the position of Finland is further away than any other from a nordic country cluster. Or Switzerland has obvious subgroups related to language (panel b of the figure, viewable from the reference). Unfortunately the sample size was too small for the Southern countries and the Balkans (I think 4 for Greece and Turkey for example), so the clusters are not trustworthy.