Well, your mod_rewrite code should work ... despite the four pedantic things I find objectionable with it. Of course, that assumes an Apache 2.x server and a test URL of precisely hostname/en/guides?country=275 AND that mod_rewrite is enabled and operates out of the .htaccess file (standard).
Do you have any other mod_rewrite before this which could hijack the URI (using (.*) where it's inappropriate leads me to believe that the answer is probably yes). If so, please display ALL your mod_rewrite code so the conflicts can be uncovered.