Indeed, I think you nailed it, happiness is so subjective as to be almost impossible to define, except maybe in those things that reduce it or cause stress.

For me it is the absence of anxiety, not the pursuit of more, or better or anything extra, I am base-line happy until something disturbs my equilibrium and pushes me out of that state.

Sometimes that push as a root from within and that's the subjective bit, but there are some externals that could contribute, like the social norms in the US you name for example.

Each of those , in my mind, increases the background stress level, I mean, do I want to live somewhere where everyone feels they must own a lethal weapon, and why do they feel that way, is there a pervading sense of fear ?...just as a simple example.

On a side note, I was in Copenhagen for a couple of days last week, loved it! :-)