Indeed - the U.S. has some of the most extreme health differences between the top end and bottom end of the income spectrum (roughly correlated to class). At the top end, the outcomes (and health measures) are better than anywhere in the world, while at the bottom end they are below most first-world nations:
For an apples-to-apples comparison, one must look at the corresponding distributions in other developed countries. It could be that the poorest people live significantly shorter lives in other countries but that the middle do better than in the states.
If you have any data about similar distributions for other countries (life expectancy by income) I would be very interested - I have not managed to find similar.
http://www.equality-of-opportunity.org/health/