Compare similar cultural groups (American’s with Swedish, Norwegian, or Swiss roots, and I bet you will find the index to be comparable.
I notice nothing on the survey to compare freedom of action, to keep what you earn and dispose of it how you wish.
These surveys are designed to make particular political points.
Ding, ding, ding! We have a winner!
Give me an hour or two to come up with some suitable survey questions and I'll show you that North Korea and Zimbabwe are the two happiest nations on earth.