On howrse, there are many servers and you can pick whichever one you want. Servers are divided into Europe, International, America, Oceania, an one with Arabic language. The 5 categories split down even more after that into an assortment of different countries. Depending on which country you pick, the game will be in the associated language. This is so that people who don't speak English, which is the main language of the game/ language of international, can enjoy and play the game as well. Also, each server stands alone and two accounts from two different servers cannot interact. This also means you can "legally" have one account on each server if you wish.
United Kingdom Howrse
You forgot U.S.A, dummies. :p