It's obviously up to you how you spell things in English, but why do you draw the line at alphabets? I've definitely seen diacritics used in some proper nouns i

It's obviously up to you how you spell things in English, but why do you draw the line at alphabets? I've definitely seen diacritics used in some proper nouns in English texts for which I have no reason to suspect diplomatic/political pressure. As I see it, you either oblige with the Turkish government's request to use the Turkish instead of English word for the country (which is what it really is), or you don't – it has nothing to do with alphabets. Whether people will practically go through the effort of setting up their keyboard layout in a way that lets them type it is a different story; I can't really blame anyone for not doing so in a casual context. Wikipedia usually does so – e.g. they currently use "Turkey", but would likely use "Türkiye" if they were to adopt that.