why can't i get MDP's books on kindle in the US?

The title kind of explains it all. I noticed I could get them if i was in another country.

Can't speak for MDP personally, bacchus, but it's usually down to international rights: basically US publishers haven't bought the rights for ebook/Kindle.

Happens a lot here in the UK: lots of books available in the US/Amazon that I can't buy for ebook here.

Annoying, isn't it?

Mark