Life expectancy differences in Mississippi vs. the UK is largely due to race. Mississippi is about 36% black, and blacks in the US have a 5+ year shorter life expectancy than whites.
Because if there's no discrepancy, or a smaller one, it seems to suggest that maybe GDP and square-footage-of-your-house is actually not all that important.
Could you clarify further if you meant one of these, or if you meant something else that I was not able to pick up on?