Oh and something else. Because the high birth rate of many Latinos that immigrate to the US, the average height more or less do not move. Statistically, that can be case for Western Europe, where we do observe very tall young white people, but the average remains the same. The reason being, the immigration from the Middle East and Africa.
Now, the case with Eastern Europe is profoundly different. A good 95% of the population is and has always been white caucasian. These countries are highly reluctant to accept new immigrants. I guess you all have heard how Hungary treated refugees. In formal Jugoslavic countries (Serbia, Croatia to name a few) there is pretty high sense of nationalism and people are proud with their Christian heritage and believe that immigration from the Middle East will harm their societies, so they don't accept any.
Because pretty much only white caucasian people participated in the sample, the increase in the average height is so evident in Eastern Europe. The same increase is also evident in Western Europe as well, however, the societies are so much more diverse and this diversity brings the average down.