Why should be Apple only selling 3G iPhones in the USA? That's something annoying. In fact, one of the reasons Vodafone gave it up was because althought it's in almost all of the countries of the European Union, iPhone hasn't got 3G and Vodafone has inverted lots of euro millions in developing their 3G network.
In fact, in Spain, where I live 3G from Vodafone is really much better and very much developed than the principal carrier in Spain (Movistar, the same propietaries than O2 in the UK).
As a result of this about 85-90% of people in Spain are able to access the Vodafone 3G network, that works in all the territory also with HSDPA and HSUPA, while Movistar only works with HSDPA and HSUPA in cities where the population is over 100000 people.
The most probable thing anyway is that Movistar brings the iPhone to Spain (it has already done throught O2 in the UK), but I don't think European carriers are very happy they miss lots of euros in developing better networks and iPhone only works with the "old" ones.