I've read a few threads as well as the Google requirements for changing the country in the Google play store. My question doesn't pertain to actually changing countries, it's about how the play store distinguishes the available apps to download.
For example, when using a VPN to the USA(current play store is UK) I am able to download Venmo(which is not available in native UK play store). However I am not able to download HBO GO(which is available in the native USA play store). Why? I imagine some apps are only available if the native app store is the specific country (where a payment card is required, etc). Are there further aspects aside then IP that PlayStore looks at? Does the app developer play into the requirements?