The main difference is that the request to change the English spelling from Kiev to Kyiv came from the Ukrainian government. As far as I know Japanese or German government haven't requested that we stop writing "Japan" and "Germany".
The closest current example going on right now is the Turkish government wanting to change the English spelling of their country from "Turkey" to "Turkiye".
It went beyond official names of cities. Supermarkets actually changed the spelling of the Chicken Kiev to Chicken Kyiv. (But left Bombay Potato and Chicken Madras unchanged, even though Bombay and Madras haven't been called that for decades.). Zelenskyy probably has better things to do right now than dictate the spelling of breaded garlic chicken fillets.
> As far as I know Japanese or German government haven't requested that we stop writing "Japan" and "Germany".
Because they know it would be silly. Do they go to every language and ask for a change? For instance ask France to stop using “Allemagne” and use Deutschland instead? Now repeat for hundreds or thousands of languages… not only would it accomplish nothing, it is pretty disrespectful to demand of the other language users how they refer to places.
The closest current example going on right now is the Turkish government wanting to change the English spelling of their country from "Turkey" to "Turkiye".