1. Average != Average. They are not necessarily equivalent, certainly not in this case - the 'average' American has a different number of kids and way more possessions, but less of an education than the average Brit...
2. You don't define what type of average - mean? Mode? Median? Geometric mean?
3. American is imprecise. I presume you mean 'den^H^H^Hcitizen of the USA', but that can't really be inferred from 'American' - it leaves 2 continents!
4. You seem to be comparing 'educated' with 'average', which is unfair. Take a US citizen and a Brit with equivalent qualifications and compare them, otherwise you could be comparing a University professor with some random scally from the back streets of Liverpool!
5. Americans don't speak or write English. There has been a fork, and the languages are sufficiently divergent to be considered different.
6. Finally, your impression is wrong.

No offence...