You don't need to speak the local language to live and work some place. I wouldn't be surprised if the majority of migrant workers (temporary or permanent) around the world are unable to speak the local language upon entry.

That works in America and the UK because there are already large immigrant communities for you to arrive into. If you arrive in Japan speaking Spanish or Hindi today, how's that going to go?

It's not impossible, but it would take a lot of time and Japanese culture isn't exactly known for xenophilia.

It’s completely possible. Most people in e.g. Qatar can’t speak much Arabic. The most common languages spoken in the Gulf are Hindi and English.

I doubt that Japan will be going in that direction any time soon, but if they wanted to, they could.

The xenophobia is the point of the reply I assume. Financial life isn’t that great for most of the world. People will go places for a better life. Language isn’t going to stop that. Xenophobia will.