Living in a country where the vast majority of the citizens speak English and a country that is so large can lead you to think that almost the whole world speaks English. Although English is certainly the most international language, you can't expect everyone to be able to speak it well, especially in a country where that is not the official language. Many American tourists have a hard time understanding this concept.
If you are traveling to a new place, consider learning a bit of the local language. People will really appreciate it if you can say hello and ask how you are.