I'm using Blockless as my DNS provider at the moment; haven't had an issue with it so far, but after numerous pieces of really helpful advice from people it seems that might indeed be the issue. I'll let you know how I go with that test! Thank you!
Well SmartDNS services are basically DNS services like the ones Google is providing but in differentiation they also enable 'smart actions' to manipulate a little bit. The 'manipulation' is set by the provider for each site and often even each device. That's why maybe HBO Go is even accesable in the browser with your US proxy set but not on Apple TV.
Blockless has a heavy price tag and I wasn't convinced by the selection they are offering some time ago. I would suggest, talking to the support on Blockless if you want to stay with them or if you are commited to a subscription. Otherwise I can recommend adfreetime for only 2$ a month. UnoTelly offers even more channels than adfreetime for also 5$ a month but I think that you will be fine with adfreetime's selection.
So yep, getting the country restriction error when I remove the proxy, so I guess that's the issue? Weird that it wouldn't be affecting any of the other apps. Both my DNS options with Blockless have been tested and do not work; just a matter of waiting it out, do you think, or time to find a new provider?