I am a bit confused as to what you are trying to do. They do let you make purchases outside of the US. If you look at the bottom of the iTunes store page there is a way to change the country.
Or are you talking about being in lets say the UK and buying music from the US store?
DRM has nothing to do with it. Ebay is also a bad comparison because Ebay is not selling you a product, other people are selling it to you through Ebay. Then there is also a difference between selling a license and selling a physical item.
Why doesn't iTunes allow you to make purchases from outside the country? I know there's a trick to do so by having a registered address within the country of purchase which corrospondes to the iTunes Store Country, but I just don't understand why this isn't allowed?
The music is already DRM'd and heck, I'd be willing to pay $1.49 per song if I could buy a song from another country using a US address. Doesn't eBay do that as it is?
I'm just saying because there are songs on the UK and Germany Store I'd love to buy, that are not offered in the US.