From BBC capital:
Native English speakers are the world's worst communicators
In a room full of non-native speakers, ‘there isn’t any chance of understanding’. It might be their language, but the message is often lost.
... “A lot of native speakers are happy that English has become the world’s global language. They feel they don’t have to spend time learning another language,” says Chong. “But… often you have a boardroom full of people from different countries communicating in English and all understanding each other and then suddenly the American or Brit walks into the room and nobody can understand them.”