Britain, or at the very least England, is also well known for its extreme politeness culture. Also, it's not that the US has a culture of genuine politeness, just a facade of it.

I have only spent about a year in the US, but to me the difference was stark from what I'm used to in Europe. As an example, I've never encountered a single shop cashier who didn't talk to me. Everyone had something to say, usually a variation of How's it going?. Contrasting this to my native Estonia, where I'd say at least 90% of my interactions with cashiers involves them not making a single sound. Not even in response to me saying hello, or to state the total sum. If they're depressed or in an otherwise non-euphoric mood, they make no attempt to fake it. I'm personally fine with it, because I don't go looking for social connections from cashiers. Also, when they do talk to me in a happy manner, I know it's genuine.