It depends on whether or not you are a male or female, how old you are and what particular things in life make you happy as to where the happiest place on earth is. I can say that there are certainly places that are unhappy, such as the continent of Africa. Also the Middle East countries, at least for young, white, American Christian males seeking female companionship...for some reason they lose their minds, including their heads over things like that. Perhaps it is the infidel thing. Asian countries just are not that happy a people, especially the Chinese and Japanese. So we've carved out a huge swath of territory that is not all too promising. Although, there are diamonds in the rough everywhere if you search hard enough and are willing to accept the culture you are in.
Now if you are a young American male in the military in Germany then that is one very happy place. The French are quite uppity. Spain is nice, at least the women are, but like all the places--the men are not so hospitable because of that fact. But obviously that is different for women. Italy is fantastic. Virtually all of Western Europe is splendid if you love history, art, architecture, drinking, outdoor cafes and brothels,and really interesting fun loving people which are all of my favorites.
As for South America...Mexico -- if they were so happy the people would stay in Mexico, but the national past times have become beheadings, drug trafficing, kidnapping and human smuggling. But then there is Brazil and Argentina. Brazil has some very happy people, but that is because of the "Brazilian Bikini" (which is a purely male chovanistic position I know!!) and the economy is doing well, plus the Obama administration gave them $2 billion to drill for oil, which I'm certain more Americans would have been happier with the $2 billion spent on oil production in the US.
Personally I had a fantastic time in Western Europe, but never made it to Eastern Europe...But I believe the Eastern Europeans are still pissed off because of the Russian occupation for 70 years. But hey, former commies want loving too!
But in the United States... it has to be New Orleans. It is party central USA. But in general, where ever I have lived I have found people to be genuinly kind and happy if you show them respect, attempt to speak their language and are interested in their culture and finally a great smile and an open hand always puts people at ease.