When I first set up my iTunes account, I didn't have a credit card, so I set it up as a US account, as this was the only way I could create one without a card (and thus use my iPod Touch).

The downside of this is that now that I am trying to add a credit card to my iTunes account, I can't, because it insists on a state and zip code for part of the address, which my Irish credit card obviously doesn't have.

So how can I switch the country of my iTunes account?