It is an interesting question. I believe that a lot has to do with the amount of time that we can devote to climbing. When I go on a varsity climbing trip I may suck a bit in the beginning, but by the end I'm finding my groove and am able to push grades a bit. Also surrounding yourself with good climbers and dissecting their technique helps, something else we may not have time for.
If you're getting paid to climb you have a huge advantage, and America has the money to do that so they can produce more 'hardcore' climbers. It's not to say that South Africa has less talented climbers, we may have the same, or more. It's more that South Africa doesn't spend as much money on them (true for a lot of sport I think).
As to the super hard routes being opened up maybe it is similar to the Flynn effect in IQ tests http://en.wikipedia.org/wiki/Flynn_effect
, which is the year on year rise of IQ scores. I'll let you draw your own conclusions from that
See some of my climbing videos and other uninteresting stuff here: