The median at any snapshot in time is materially better off, but also much more stressed out than people in other wealthy countries about whether they might end up in a very bad economic situation, due to how there is barely any bottom. Subjectively, middle-income Americans don't feel well off and don't feel secure in even what they have. For example, numbers vary based on the specific survey, but about 60-70% of Americans consistently feel high levels of stress about money. I'm not sure that's a course that would've been taken by a 50th-percentile person trying to optimize their own well-being?
One reason Scandinavian countries tend to come near the top of those "happiest countries in the world" surveys (though I don't like the term "happy" for it) isn't from any particular joyfulness, but because the typical household subjectively has very low levels of economic fear or stress. Some of the survey questions that go into that score include things like, do you feel economically secure, do you worry about losing your housing, etc. A huge percentage of even middle-class Americans spend a lot of their time worrying about that (including my family), while the majority of middle-income people from say Denmark don't consider it a big risk to worry about.
The US has consciously made that trade-off. See how even Sanders doesn't propose to raise taxes on people making under $250,000, and Biden is up at $400,000. The top income tax rate in the Scandinavian countries kicks in at around $70,000.
It’s not dissimilar from that of Germany (0.935 vs 0.939), and it’s higher than that of most other OECD nations.
As for average life expectancy: the average is brought down by outliers. In general, the US has a higher homicide rate, a higher motor vehicle death rate, a higher obesity rate, and a higher opioid/drug death rate. These external factors all bring down the average life expectancy number more substantially than in other countries: https://randomcriticalanalysis.com/2017/05/16/the-explanator...
Even if you assume the lack of a safety net causes the symptoms above, my point is that the lack of a safety net is deliberate, because even our left wing party promises not to raise taxes enough to actually fund a more robust safety net.
Apart from that, the life expectancy of white Marylanders is 80 years, just a bit shorter than for Germans (80.9 years). But 30% of our state’s population is from a minority group that was enslaved on Maryland plantations, and then denied civil rights until very recently. If bill gates had been born in the county where I live as a Black kid, he would have gone to a segregated school until middle school. Their life expectancy is several years lower, due to the legacy of those injustices.
Many of the differences between the US and European countries are misdiagnosed as matters of general policy (safety net, healthcare). But when you break it down, much of the difference is actually the result of the country’s history and large Black-white gaps in many indicators. The median white household, for example, has 10 times the wealth of the median Black household—a fact that plays a huge role in people feeling economically insecure. But those gaps can not necessarily be fixed with the same policy choices that European countries apply to their general populations. That wealth gap, for example, has not changed since the 1960s, when Maryland schools were still segregated—despite a large growth in general social welfare spending since that time. It is a unique challenge that requires targeted solutions, and there is no political will to implement those policies. These policy challenges simply have no parallel in Germany.