Are there any advantages of being bilingual beside being able to communicate with more people? Most anglo-countries are monolingual, and they are doing quite well.

People from Switzerland and Luxembourg are usally trilingual, and they have the highest HDI in the world. However, you can probably find many examples that prove the exact opposite also. People in India usually speak many language, but it doesn't seem to be of any advantages to them. The examples I gave are extremely binary, and there are other variables to take into account of course.