Completely relate. I'm from a nation of professional weather-chatters, and here my friendly bus-stop comment gets a polite nod and nothing more. But invite me in for coffee and suddenly it's two hours of real conversation. The warmth is just kept for the inner circle.
Where I'm from you chat to everyone — the cashier, the person in the lift, strangers at a bus stop. Here that same friendliness gets me confused looks, like I've broken some rule. But then people are incredibly warm once you're actually introduced. Did anyone else have to relearn the whole small-talk rulebook?