Japanese students learn English. I learn American English in the text book at school. There are many countries where people speak English in the world. I think American English has changed, especially pronunciation. U.S.A. is a very big country and there might be many dialects. Australian English is different a little from American's. Singaporean, Hongkong people, East Indian or Philipino also speak in English. I think Canadian English is easier to listen for Japanese people than American's. Is British English standard of them? I didn't learn it at school.
Even in the small country, Japan, we have a lot of dialects unbelievably and then decided standard Japanese to learn at school.
Standard English in the world should be made. The world's common language is English but I can't chose which country's to learn. I felt troublesome.