Talking to strangers. As a tourist in the US, I had so many people in public just randomly start talking to me, just to pass the time. On a bus, crossing a car park, whatever. Just chatting to folks. They'd then hear my accent and the conversation would steer that way, but they still broke the ice first.
I did mention to someone that it was only men doing this, and they said that American women do it as well, just not to solo males (for obvious reasons). But with other women or a mixed couple, they'll break the ice with strangers as well.
I haven't encountered that in any other English-speaking country I've been to. Not at that frequency, anyway.