BLURB
Let's face it - it's cumbersome to search for long country names (e.g. United States). It would be save a significant number of key strokes, to include in the country search list, the 2- or 3- digit ISO country code and show this country first in the results (e.g. US for United States, or CH for Switzerland), so one does not have to choose between all the countries containing "United" (USA, UK, UAE, etc)

COST-BENEFIT TRADE-OFF
- Need to update UI for all apps (Windows, Linux, Mac, Android, iOS (well I know it applies to Linux, so maybe some can be crossed off))
+ Base functions (at least in the GTK application) already are using ISO codes to pass to base connect functions
+ Should be pretty quick to implement - for GTK probably changes would be fairly contained to one file - https://github.com/ProtonVPN/proton-vpn-gtk-app/blob/master/proton/vpn/app/gtk/widgets/vpn/serverlist/country.py
+ Saves a significant number of key strokes (estimate would save approx an hour of typing over the course of one years for a user connecting every day at 3s longer to type full country, multiplied by 1 million users, that amounts to 100 person-years saved*)

SUPPORTING INFO / REFERENCES:
- Full list of iso country codes on https://www.iso.org/iso-3166-country-codes.html
- https://www.youtube.com/watch?v=r7yhxoqffD0: UK or GB? - Why Every Country Has A Two Letter Code (fun video, for a boring day)
- https://www.sporcle.com/games/hkthom/most-common-3-letter-sequence-in-countries-of-the-world

• This is a back of the envelope calculation, see xkcd for further justification/examples of such estimation techniques

P.S. It looks like front-end apps are open source, perhaps could be taken up by the community (perhaps create an issue with it and tag as up-for-grabs, to get attention of potential contributors)