People sometimes have good time (better than avg), sometimes bad time, and sometime neutral time (say.. thinking about some problem to solve, or repeating Swedish vocabulary to learn a new language, or trying to recall the name of a person you just met and you're supposed to remember).

If you're compelled to smile with every interaction, in order to show that you have good time, then it'd mean that you'd be mostly lying according to the aforementioned definition :).

Unless we re-define the 'good time', so it means 'not significantly bad', which seems to be the case here. It's just, that it requires a bit of effort to remember and to switch to when visiting US.