> showing a map of Europe that includes Ukraine but excludes Russia - a choice that I think is likely to have been influenced by politics, since I am much more used to seeing Europe defined as extending east to the Ural mountains and there is no geographic reason to draw the border of Europe along the Ukraine-Russia border.
The politics might be milder than you're thinking; some people find it awkward for a country to be partly in one continent and partly in another. Russia obviously can't be included in a map of Europe - only the European part of Russia would make sense. (As, indeed, you advocate.) If you're making your map by including countries, as opposed to regions, you'll have no choice but to leave Russia out.
A similar issue of confusing continental boundaries, political boundaries, and ethnic boundaries can be seen in the various claims that e.g. Cleopatra was black. The logic goes that Africa is populated by blacks, Egypt is in Africa, and Cleopatra was the queen of Egypt. (You see the same thing about various Berbers who were active in the Roman Empire.) It never bothers these people that the words "Africa" and "Africa" in those three correct claims do not mean the same thing, or that Cleopatra was not an Egyptian. She was notable in her day for being the first (and last) member of her dynasty who was able to speak the Egyptian language.