Americans were the tallest people until the 1950s because:
1) the USA was the most prosperous country in the world until the 1950s
2) they received a lot of immigration from listed above "tall countries" in Europe
So while having much better nutrition than most of Europe, they had similar genes.
Take for example Norway - it was a poor country during the 1800s and early 1900s.
Domen, you are dividing by language, not by ethnic/genetic groups.
Dividing by genetic groups is impossible if this data is for entire countries.
I presume that 176 cm for Russia (in year 1992) is less than average for ethnic Russians.
Some of Non-Russian minorities, especially those in Asian part of Russia, are not famous for being tall.
Wikipedia also has no data for Ukraine and Belarus. Belarus is probably rich enough to have good nutrition, Ukraine is poorer.
North and South Koreans have vastly different heights, as the North is a starving communist hellhole.
North Koreans are genetically practically the same as South Koreans, so in this case nutrition is responsible, yes.