As an American in the UK, I’ll chalk it down to cultural and historical differences. I also suspect there is a cynicism and hostility about mankind and religion because so much of the country’s history is filled with wars and bloodshed over it. I think Americans probably forget that the British had a pretty rough go of a lot of things on their own soil in ways we haven’t and probably don’t understand.
I do miss some of the open friendliness and kindness to strangers that you find in America, at least I don’t experience it much the part of the UK I’m in (England). People tend to be more reserved, though they will open up after a while. But the reserved nature does make for more reserved and respectful liturgies, which I enjoy very much.