This is a neat website run by the linguistics program at my alma mater.
accent.gmu.edu One of my English professors directed me here after reading a Shakespeare play and noticing that Shakespeare liked poking fun at the Welsh accent. In the past, I had despite having both a Welsh cousin-in law and English one unable to tell the difference between the two accents. You definitely do pick up an accent if you live somewhere for a while. The guy who taught my Irish film and lit class in Ireland was an American but had a slight Irish accent due to living and teaching there for twenty years. And my cousins who married the Brits have that a little and use British slang. I don’t see their kids enough so I don’t know whether their kids sound more British or American or a hybrid of both.