the US is being deprecated:
http://blockchain.info/nodes-globe
That is the numbers of nodes , not hashing distribution
http://blockchain.info/nodes-globe?series=topBlockRelay
this tells a different story than the title.
Also , the number of nodes have decreased to 90k from 200k+ in May.
http://getaddr.bitnodes.io/
then what do the height of the spikes represent?
I think it represent the number of node in that area. Not quite sure though...