The question at hand might seem like stupidity to many people out there, but this is a question that is very understandable if you have been working and using Netflix for a while. Because with one Netflix subscription you can easily watch Netflix in both the USA and in the UK, it is all a matter of your current IP address. In other words, if you have an American IP address you will automatically be sent to US Netflix, while you with a UK IP address will be sent to UK Netflix. And you do not need an extra subscription for this to work, but you automatically get access to the content of the country you are currently in (with your IP address). And that is why it is a really good question to ask: “Can I use my UK Prime subscription to watch US Prime content?”
That was a long introduction to this article. Hope you are still with me. So, the question is valid, but the answer is short: NO!
That is for sure one of the great things with Netflix where it comes as a big bonus, while it is kind of natural that it is not included. In other words you will need to register a new account in the UK (if you currently have a US account) and then sign up for Prime there, or sign up with an American account (if you currently have a UK account) to watch Prime there. Do not forget to register your new account at the right Amazon shop (Amazon.com if you need an American account and Amazon.co.uk if you need a UK account).