I've been involved with this crazy podcasting thing since April of 2005. One of the things that has always stuck out with me is the amount of Australians involved in podcasting or listening to podcasts. It's been my experience that while a lot of technology doesn't necessarily have its roots in the US, many technologies receive their first burst into the light from VC marketing money in the US.
It's interesting that podcasting has taken off in Australia and arguably the UK before the US. Not a very common occurance in this part of the world.