This is a problem that mainly affects people from non-English speaking countries. You search for something in your local language and get results from American-centric subreddits translated into your language, which may not be relevant to your query at all.
If I'm searching for "szpital" (Polish for "hospital"), I'm not interested in results about the American hospital system. Not to mention that the quality of the translations isn't always good.
Anyway, there's a workaround, add this string to your queries: -inurl:?tl=
Automatically translated Reddit posts contain "?tl=<language>" in their URLs, and the helpful "-inurl:" operator allows to filter out the results that contain this string.
