There is no difficulties for Amazon to start accepting Bitcoin payments and there were rumors about them accepting Bitcoin a long time back when other online shops started accepting Bitcoin but nothing happened and so is the reason other sites that started in order to take care of that and purse.io was a major site everyone used for a long time to purchase goods from Amazon and till now there is no updates whether they will be accepting cryptocurrency but i wont be surprised if we see them coming out with their own cryptocurrency.