It could be genuine of course but they won't ship to Europe directly (or at least not through amazon marketplace) so you would need to get some friend or intermediary service to send it on and if it wasn't genuine I can only assume this would be again more hassle which is why second hand route is fine for me.
I assume there is only one model so the american phones would also work in europe.
The other reason I was a bit skeptical is there are a huge number of fake N9 phones on eBay and I would imagine that there cannot be that many new phones left at this stage.
However I'm not sure if Amazon will cover marketplace in all cases which is understandable from a business point of view. https://payments.amazon.com/sdui/sdui/about?nodeId=6120
I had a look at the offer from wireless everything and I must admit it seems above board on first glance at least. The only strange thing is that the price is 200 dollars more on their own website. If you do go down that road it would be interesting to know if it's genuine as I have a friend who has an N9 but he said the battery is no longer what it was and he's afraid it will break when he tries to replace the battery and may consider picking up second one as a spare while they are still available.