Does that mean you think it's useful in English-speaking countries?

As long as 70 years ago the US census bureau found Soundex was useless for analysing their early (first 30 years) census records and changed the algorithm; now the US government publishes its own encoding rules, which may be the same as the original Soundex rules (but I doubt it). There are rather a lot of better phonetic fuzzy encoding algorithms, and the name is widely misused: most things that are called Soundex are not actually Soundex.

I don't know whether the Soundex in SQL Server is the original Soundex or not; if not it still shares most of the failings of the original - enough to make it not useful unless augmented by other matching and distinguishing techniques even for names in English-speaking countries.