As has been mentioned, the country-list is only a list of countrys where the N9 will be sold "freely" from the start.
Norway (where I live) is not on the list because it will be (initially) sold exclusively through one operator, Telenor.

So, chances are that there are allready exclusivity contracts in place in most of the countries NOT on the list.
US not being on the list could be because Verizon (or some other Operator) allready has exclusive distribution rights :-)