Apple TV+ Language

You can change the audio language (and/or activate subtitles), from the text balloon icon in the lower right corner, when clicking in the viewer window during playback. That icon should give a pop-up window with the available audio streams and subtitle streams. Just like in Quicktime Player. Just like in iTunes before.

I have a similar question to the OP. Is it possible to change the homepage language and menus if you are using AppleTV+ outside the country of registration? Example, I have a Dutch AppleTV+ account which shows all menus and descriptions in Dutch. However, I am using the app in the US and want the menu and descriptions displayed in English. Is there a way to change the default language?