Not sure that every browser advertises English, but mine certainly does. However, as I'm in Portugal, many websites ignore what my browser says and send me to translated versions, I assume based on my IP. That causes problems because the translations are often quite bad, and they do it with redirects to PT URLs so I can't share links with people who don't speak the language.
Does "advertises" in this context mean what's put in the "Accept-Language" HTTP header? Might be worth seeing what that value specifically is the next time this happens. A "clever" IP-based language choice server-side seems far too complicated and error prone, but I guess that's what makes it so "clever."
I have the same problem in Argentina. Worse, I'm pretty sure that Google and other search engines decide that I don't deserve to receive good information because I live in a Spanish-speaking country, so they send me to terrible low-quality pages because often that's all that's available in Spanish.