In the absence of high infant mortality, it isn't clear to me why median and mean for lifespan would diverge in any meaningful way. In the presence of high infant mortality, the mean would just be lower than the median: how would that be particularly informative?

Median and mean could and most likely do diverge because poor people live significantly shorter lives than rich/middle class people. Europe in general is more equal than the U.S.

The mean would give the same quantity of information but biased (in this case) by the infant mortality rate, which probably should be examined seperately. The median is the preferred statistical standard.

What you are looking for is a distribution of life expectancies per country.

"the median is the preferred statistical standard" - that depends, not sure what this blanket statement means. But yes, you are right, I am looking for the distribution or a sense of it anyway.

I posted this comment elsewhere, but I thought I'd try it in an active part of the thread to see if anyone can answer my question: Do the OECD averages reflect population weighting, or does, say, Belgium count as much as the entire United States?

You'd really want to see something like a lifespan version of the Gini coefficient to assess inequality. Having the mean as well as the median wouldn't really tell you a lot.