Yes you can, and that has been standard practice on the Internet since forever.

Things are much better now with Unicode etc., you will still run into problems with things like directionality and non-Latin scripts all the time.

If English is the default language and if English support is always the highest priority compared to every other language, that’s effectively the same as saying “you can’t speak your language here”.

And it works the other way around too. If you build something local and support only the languages used locally, you’re effectively saying to everyone else, “you can’t use your language here”.