Approx. 5 years ago, I spent a year in Canada as an exchange student, and noticed the same thing. Everyone was happy, smiling, outgoing, never showed any sign of sadness. At first, I found it uplifting, but as time went by, I started to feel a bit anxious. I felt like I had to act like everything was fine all time, even though everything never is fine all the time.
I live Finland, and I find that people express more of their emotions here than in North America. Somehow it's good, but sometimes it isn't ideal either. When people feel they have the right to be sad at any time, they aren't willing to make any effort to feel better. For some, it's an ongoing vicious circle, and it's quite hard to be a bystander...
However, thank you for this though provoking post, it's important that people address this problem!