If you lived on a border of a country that speaks different languages how is it chosen what language you speak? If you lived on the border do you just learn both languages?
Or is it more if you lived even like 500 meters of a border do you learn the language of the country your in? Do people choose it based on nearest popular city to where they’re at?
That tends to be how it’s done. States tend to be rather protective of their official language, and it’s generally impractical to send your children to school in a different country. Being somewhat proficient in the other country’s language is quite common, but to truly be bilingual you pretty much need to be some kind of ethnic or religious minority.
Also depends a lot on the relationship between the countries and languages; some borders are easier to cross, and some languages easier to learn.