[John_Innocent]

I don't know but if I had to speculate, I'd say the US has less efficient government, because of factors like greater wealth (more complacency toward waste and corruption) and a larger and less homogenous population (a less coherent public debate).

With respect to the second point, I hypothesize that generally central economic planning becomes less efficient as the economy it plans grows larger. I suspect this is related to Dunbar's number.