I have a googleTV device running on a 2017 Samsung TV. In the last few months all of YouTube is slightly zoomed in. I watch a lot of gaming videos so I notice it. Any game video that has information on the edges of the screen is cut off.
I have searched everywhere to find an answer. There aren't any settings that I can find in thr YT app or on the TV menu and nothing else seems to be affected by it other than YouTube and only while playing videos. The YouTube App menu is fine, edge to edge.
Search google for overscan + your model of TV. There should be an option to disable this.