I live in Canada and I speak English.
I got a Chromecast with Google TV right when they were first released. Since the beginning, it's pretty common for the thumbnails on the main screen to be in another language.
Here's an example.
I've seen a lot of what looks like Spanish and German. It's not only 1 language.
I reached out to Google TV support, which wasn't helpful. They told me to use my remote and say "send feedback" to the Google Assistant. I have sent feedback nearly every day for half a year on dozens of shows and movies. There's 0 evidence that it's going anywhere or that anyone cares.
Does this happen to others?
Have you poked around in your Google account settings using a web browser? Maybe you have language set to English (UK) or some other English variation that isn't US or CAD. Typical Google though to just leave you in the lurch with no resolution. This should have been an easy problem to solve on their end.