It feels odd giving this a lukewarm review. This is actually an incredibly difficult film to critique because one feels forced to look at it from perspective of the fan as well as the outsider. And there doesn't seem to be any "casual" fans of the On Cinema at the Cinema Universe, a network of media and shows that is so deep and winding at this point, it would be futile to attempt to explain in the confines of something like this beyond saying "it's a spoof of Siskel and Ebert" (and even that feels like too much and too little).
Personally, as someone who's consumed every second of the endless nonsense that is On Cinema etc., this felt a little flat to me, like they finally drove a joke into the ground beyond recognition. Perhaps, the restraints of the mockumentary format, which beckons for legitimization by attempting to unpack that aforementioned extended universe, a seemingly impossible task for the uninitiated and redundant for the believers. That isn't to say this isn't an enjoyable film. It has some great moments and any extra time spent in the world of these characters is never a waste. Especially Gregg, who--in perhaps a setting as far removed from Movieland as ever--still brings it back to his VHS tapes and popcorn classics, imploring the filmmakers to study the 1976 Disney flick The Shaggy D.A. to better understand what's happening with Tim (but to make sure to return the cassette when they're done). It's great.
Mister America also provides closure for the best thread On Cinema has ever stitched: The Trial. And maybe that's also where it suffers. The Trial was such a special landmark; it might never be topped. But the one thing we know is that Tim and Greg and company are always gonna try. By any means (or medium) necessary.