In Thinking Fast and Slow, Kahneman talks about an experiment where they had people answer a quick questionaire about their immediate emotional state throughout the day, kind of like sampling. Something like are you stressed, angry, happy, etc. at this very moment. If I remember correctly, the results showed that most people are fine most of the time, but a small number of people are in constant emotional distress.

Sure, have a look here:

https://ourworldindata.org/happiness-and-life-satisfaction

The second chart of the page shows the share of people who say they are either very happy or mostly happy, click on "Map" in the bottom right corner to see all the countries for which data is available.

Sample: US: 90 percent say they are happy China: 85 % Ethiopia: 63 %