With Google, I'll install an app while in the USA. Then when travelling, I'll get a notification that there's an update available. But when I go to update it, I'm told the app doesn't exist. This is actually a security hole: If I have a buggy app, I can't update while outside the US.
If I sign in with my Google account, nothing changes - I'm still given "local" content. This is why I don't bother with Google Music. I'm not interested in having my files disappear to "not available in your country", despite using a USA credit card and address on my account.