I agree with Greg on language. Having different languages enriches the world. There are different and often unique expressions in each language.
Besides, I've been in neighborhoods, or countryside, in Europe, and the local folk did not speak a lick of English. Fortunately, I could converse in German, or Spanish, and struggle in French, but I could communicate, and it was fun and useful. Usually when I travel to a country, I try to learn some of the language, or some phrases, with which to engage in some basic pleasantries or conduct some basic transaction. It's appreciated when a foreigner demonstrates some interest and effort in a local language.
Interestingly, I once had the privilege of having dinner on a river boat in the mountains of Shikoku in Japan. Our Japanese guide from Tokyo has a hard time with the local dialect, because it was a regional and older dialect of Japanese. The boat was operated by a local fisherman, and he and others used cormorants to catch fish. Some of the fish we ate came from the cormorants. It was a fascinating experience.
I can imagine some Americans traveling to Australia, Wales, Ireland or Scotland, and even parts of England, and having trouble with the local dialect of English. My wife has had difficulty with some dialects of English, especially from parts of Lancashire and Yorkshire, and further north.