Hi,
I put on my policies that post has been slow getting to the US recently. One of mine took just over 2 weeks.
They have really tightened up at customs on the US side that is really slowing everything down.
I have also been waiting for a couple of things ordered from America for a month. I`m not worried yet as they have been marked sent and I have been in contact with the seller.
I think if you keep in communication with them they will be reasured and their item will turn up soon. I don't know what time period I would wait until I offer a refund.
I have also learned to get a tracking number for items shipped to USA now.