I generally blame the lot of them.... I am good at distributing blame.
As a customer, the only thing I know is that they are not able to make me a customer without being fraudulent. I do not really care much who to blame, but it is their shop, they are advertising this global (intentional or not). It might be because they are only dealing with US licenses, but as long as they (Amazon) do not manage to make some fixes (i.e. sorting things out legally with publishers) I give my money to those who have managed to do so...
It is really no big deal for me, I tend to get the games I want for a price I find reasonable, but it irks me a little that that Tony_Amazon comes to a forum of a Polish based company (servers in Malta?) and speaks to "you all" when it is not legally locally to buy the products he is talking about.
They are doing exactly the same thing GOG did when they let you chose your own location when buying Witcher 2. And GOG got sued by their publisher because of it and were forced to implement real geo-location tracking.
Personally I'm against publishers who want regional pricing and I'm pro-GOG and pro-Amazon in the way they handle things. When the alternative is offering you €1 = $1 prices (or not at all for some regions) I'll take their turning a blind eye and giving you the fairest prices they can, and I'll thank them for it.
It never ends to surprise me how people bash them for being USA only and not caring about the rest of the world when actually they risk being taken to court for the customers from the rest of the world. USA customers gain nothing. Don't get me wrong, it's clear they are not doing it out of the goodness of their hearts, but to make money.
If you really have strong principles about the "greyness" of the situation I can respect that, but most people see "valid for US customers only" and think "omg, Amazon, you suck! why don't you care about me too?!?", when in fact they do care and allow you to take advantage of the best deals they can offer.