I spent 2 weeks in Iceland doing the ring road. We stopped for dinner in a tiny village in North Iceland. Our server genuinely sounded like an American. We asked if he had lived in America. He said he had never left his village, even to go to the capital. He just learned English from American media. His English was flawless. He could have said he spent most of his life in America and we would have believed him based on his accent alone.

Between schools teaching some form of standard pronunciation (in most countries, at least), and routine exposure to the same through mass media and intermingling in large cities, most languages seem to be on the trend towards less dialectal variety.