I was wondering if you get access to the same content as you sign up for Amazon Prime in the UK as you do in the USA? Or in Germany or Austria?
That is a brilliant questions, but I can at once tell you that the content you get access to is not the same. Just to give some examples I can say that the TV series Mr. Robot has been available on UK Prime since at least February in 2016, but it has not yet arrived to US Prime. It will arrive within shortly, but it can’t be seen there yet. In the same way the film The Imitation Game with Benedict Cumberbatch was made available on UK Prime very quickly, but it was not at all available on US Prime (and it still isn’t if I remember correctly). So, the answer to your question is no. There are big differences between what is made available on Amazon Prime in the different regions and nations, so it kind of follows the principles of Netflix where films and TV series are added in very different regions. This has to do with copyrighting rules probably and also the fact that there are different companies distributing the rights to show films and TV series in those nations also offering them at different prices, and that is how things look differently in the different Prime regions.
Now, if you are a maniac and really want to get access to all the different Prime regions then you can of course create an Amazon account in the different regions and buy an Amazon Prime account in the different regions, and then you can use PureVPN to get an IP address in the nation in which you actually want to watch Amazon Prime.
The principle here is that to watch an Amazon Instant Video or an Amazon Prime video in the United States you will actually need to have an American IP address. So your Amazon Prime membership is in itself not enough, but you also actually need to be present, or at least virtually present, in the USA. To watch Amazon Prime in the UK you need your membership and of course a UK IP address which you can also get with PureVPN. And the same is true for all the other Prime regions.