That link defines happiness as in how happy would an American hipster be with the local political situation if teleported there, not happy as in how likely is the average dude on the street to smile or laugh, or how likely is armed revolution.
For example Turkmenistan comes in near last, and it would be hell on earth for a coastal USA hipster who just wants to talk progressive politics in a coffee shop all day, but the natives kinda like it the way it is... happiness is not defined by most as a starbucks on every street corner, etc.
Truth is probably somewhere in the middle.
http://happyplanetindex.org/countries/united-states-of-ameri...