Any application that ships across borders needs a way to name a country. You reach for a two-letter code, write US , JP , DE , and move on. Then a support ticket arrives. A user in Belfast picked "United Kingdom" and your shipping API rejected UK . Someone in Pristina found no option at all. Your analytics dashboard shows a country called AN that dissolved in 2010. These bugs share one root: ISO 3166-1 alpha-2 carries more rules than its two characters suggest. Let's walk through the...