Who is impressed by a British accent?
The main significant effect found in this study was that people who’d lived at least three months outside the US rated the English accent significantly lower than people who’d only lived in the US. In fact, Americans who had not lived abroad considered the English-accented person to be much more intelligent than themselves, but the people who had lived abroad rated the standard American accent more intelligent than the standard English one. My preferred way of interpreting this (a bit tongue-in-cheek) is that Americans are happy to rate the English as more intelligent than themselves up until they actually start meeting and talking to the English.
There is more here.