From my experience it’s just part of the cultural differences. While many Americans, at least in the Midwest where I spent a lot of time for work, are very friendly and outgoing, I hardly ever got the impression that it’s deep or meaningful. From my experience it was very easy to have great conversations with people whom I hardly knew or had met just an hour ago but hardly ever did it go anywhere meaningful.

Now to the question of how does one become this outgoing kind of person: just try and talk to people, remain friendly and open. It will likely take some practice and maybe not be reciprocated by your average European.