Earlier quoted context omitted.
I think Americans are more optimistic and thus are happier. Someone somewhere said it was America’s super power, that we believe things will always get better and it creates a self fulfilling prophecy.
Not sure about the happier part, I may be wrong as I've never been to the States but it looks like the meth/drugs epidemic is a major issue in much of the US. A happy populace wouldn't need to resort to drugs.
How about instead of blaming the population, we pin the opioid addiction to big pharma and their illegal practices of lobbying and bribing their way into doctors prescribing opioids for toothaches and headaches. See Purdue.
Also, Finland is constantly rated as the happiest country in the world yet suicide rates are relatively high and alcohol abuse is rampant, so maybe that's not how happiness works.