While mooism2 is correct and flags don't mean languages, I think it's a common enough pattern on web sites that you can just choose one or the other (USA or UK)

While mooism2 is correct and flags don't mean languages, I think it's a common enough pattern on web sites that you can just choose one or the other (USA or UK) for English. But you should then be consistent with spelling. It depends on how you want the site to be perceived. As an American, if I see the British flag next to an English language selection, I'm not offended, but I do feel like the site is targeted more toward European users.