I also think part of it is that people are more attuned to being polite to people they consider to be visitors (maybe, sometimes and depending on how they view that visitor).
My general impression has been that English people are more polite and more open to interaction and conversation in a restaurant or in a line at the grocery store, etc. But English people I've discussed it with think Americans are generally more polite and friendly in casual or service-oriented situations like grocery stores.
My theory is that it's the status of visitor. Maybe we take more pains with people we feel are visiting, whether it's trying to make a good impression or assuming they may need help whereas if you're American in America, you expect that other person to know the ropes and get it done and I gather it's the same in England from what people in England have said - if you're English in England- they don't assume you need any special treatment or help, and it's not automatically forthcoming.
So maybe you do feel more catered to when you're the visitor.
But I also think that as Americans (especially on the east coast) you do learn how to get what you need and that directness is the best and fastest avenue to productivity. When you live there you recognize it for what it is and learn how to respond in kind.
New Jersey/New York people are some of my favorite people in the world. You always know right where you stand with them.
I also agree - my experience is that Italians do love Americans and they aren't hung up about sex- and they do seem to have a very nice lifestyle and general attitude and philosophy about the pleasures of life.
I could definitely live there.