As I understand it, this is linked to your device and/or account. If your device is carrier-branded, then it's tied up to said carrier's country content. If it's an unlocked device, it should be linked to the country associated with your Google Account.
Now, where I'm not exactly sure if it makes a difference or not is if you also need to be behind an US IP for the content to be available, in which case you'd also need to use a VPN or a service such as Hola Unblocker.
Of course, if none of these solutions are of your liking, you can always root and install an app that would allow you to change the Store's country content. Yup, there's an app for that. Actually there are quite a few apps for that.
UPDATE: I just tried it with my account and yup, while apps seem to be tied to my device's country because it's carrier-branded, I can unlock media content not available in my country if I use a VPN to 'mask' my IP as being from the US. So there you go, hope it helps