What is it about the English accent that has the effect it does on us in general? My theory is that it is like the whole burnt offering in the Old Testament: it is emphatic and it functions as an intensifier.
When I was in Colombia teaching English, I was exposed daily to the English accent in circumstances which cast its speakers in a light not so glowing as perhaps the Anglophile feels. And then I had an unusual momentary experience that showed me something. I heard two people speaking in what seemed to me an easy and soft way, almost kind. What was that music? American accents. It was a strange moment when what was familiar became unusual and I viewed it from without, struggling for a few seconds to identify what it was and because of that observing what I never had before.
The English accent is not as easy. I think the effect on us is of something more laborious, as if they’re going to some extra effort to say things. That is why I think it functions as an intensifier. If the English person speaking has, quite apart from the accent, a strong melodious voice, the effect on us is of someone going to a little extra trouble to please us, and if it is a harsher voice, the effect is of someone going to a little extra trouble to displease us. And that, I think, accounts for the phenomenon.