A Y-DNA (paternal) haplogroup map of Europe:
The data are very interesting since each pie chart reveals something about the ethnic composition of each country.
R1b and R1a are associated with the Indo-European population which invaded Europe from the Pontic-Caspian Steppe during the Bronze Age. This group especially made an impact on the populations of the British Isles and the Netherlands - the Bell Beaker people mostly entered Britain from the latter - with them wiping out and replacing a large percentage of the indigenous EEF males. The Indo-European steppe population was particularly warlike and barbaric. This is where the "barbarian" nature of the majority of people in the modern-day British Isles comes from.
Curiously, Spaniards also have a high prevalence of R1b, having been heavily invaded by the same Bell Beaker people, even though they are phenotypically quite different from British, Irish and Dutch people. It would be interesting to look at the maternal DNA of the Iberian Peninsula.
Italy has more pronounced genetic variation than Spain when it comes to Y-haplogroups. Only about half of Italians have R1b while significant portions of the population have J (Anatolian), G (Caucasian), and E3b (Near-Eastern/North African). Italy was always more of a crossroads due to its more central geographic position within Europe as well as its prominent role in the Roman Empire. More diverse populations immigrated there.
Greece, Albania and the Balkan countries are mostly not very Indo-European. They have more indigenous EEF, Anatolian and Near-Eastern Y-haplogroups. Interestingly, all of these countries speak Indo-European languages (Hellenic, Illyrian, Slavic, etc.). These will have been imposed upon the non-IE majority by an IE elite minority at some point during or after the Bronze Age. I personally find Eastern Mediterranean females the most exotic and attractive in Europe.
Hungary is as Indo-European (R1b and R1a) as many other European nations despite speaking a non-IE language of Finno-Ugric extraction.
Conversely, Lithuanians who form the most populous Baltic people group are less Indo-European with seemingly about only a third of the population having either R1a or R1b even though Lithuanian is supposed to be the most conservative IE language besides Sanskrit. Curiously, Lithuania has a large percentage of N3, which is a Siberian haplogroup. Maybe this accounts for the unique Baltic phenotypes which I've spoken about before on this forum.
Finns are even less Indo-European and have the highest prevalence of the N3 haplogroup as well as a significant portion of the indigenous I1a haplogroup. The prevalence of N3 corresponds with Finns speaking a non-IE language - i.e., Finnish.
Surprisingly, - and
@galii brought this to my attention in another thread -, Swedes and Norwegians both have a high prevalence of the I1a haplogroup which is native to Europe and goes back to the hunter-gatherer populations.
Turkey, although technically not Europe, has a great diversity of Y-haplogroups with Indo-European, Anatolian, Near-Eastern, Caucasian, Siberian and Central Asian haplogroups.