I’m surprised by this. In my experience, Google are the one big organisation that I can count on to get this completely and utterly wrong. I’ve lost count of the number of times I’ve been stuck with a Google interface, popup, or some other thing that is in a language I don’t speak, just because I was visiting another country. I’ve specifically encountered it repeatedly with the very Google Sign-In widget they say works for them.
Sure, if it happens to be a Google website and you know the magic incantation of &hl=en then you can sometimes work around it, but that doesn’t help when it’s a Google login from another website or something of that nature.