If you want the www.openstreetmap.org website in English, you may want to log in and visit https://www.openstreetmap.org/preferences/edit and enter “en” in preferred languages.
If this does not help for e.g. the nominatim based search, you may want to change your browsers accept-language headers. But you would have to tell us the browser you are using to help you further. If you do not want to change your browers accept-language header, you may want to use e.g. https://nominatim.osm.org/ui/search.html?q=washington&accept-language=en (where I changed the language under advanced options into “en”).
