I always feel that many in the U.S., by far my largest cultural exposure, consider a false stoicism as mature and wise.That's a trait we inherited from our cultural progenitors the British. And in general we don't take it to the extremes they do. On the broad spectrum of human cultures, Americans are fairly "chummy" and open, or at least seeming openness is encouraged. The problem is, we expect others to be open, but we also expect them to be like ourselves. So we punish people who open up and turn out to be different. So they clam up.
The best place that I have found people to open up and be themselves within a day, is at a bar. Even if they just got there and have not had a bit to drink.
You think American bars are good? Try Japanese bars. American bars, to me, are usually noisy, crowded affairs where it is difficult to even say a few words to someone let alone have a conversation. This is particularly true where I live (Boston area), where the bars are often packed for the Red Sox/Patriots/Celtics/Bruins games. But the bars I went to in Japan were tiny and intimate. Only five or six people could be in there drinking at once and it is far easier to strike up a conversation. Particularly if you are a Westerner.
Japanese society is about as serious and as punishing of individuality as it gets in the developed world. The Japanese bar scene is thus correspondingly lively and full of sincerity, even in tiny bars where there's barely any room to move your elbows.