Go to your profile or any of your own posts (so that you can see your own US flag). Click on your flag and in the address bar of your browser where it says 'United States' at the end, type Russian Federation (or whichever country you want to search) instead.
Is there not a menu of countries available somewhere? Editing the URL is a bit kludgy and error-prone, especially when countries have more than one plausible name (e.g. many people might reasonably expect "Russia" to work instead of "Russian+Federation". I notice similarly that the text name for US is "United+States", not "United+States+of+America", etc. Which makes me wonder why the ISO country codes weren't used instead, but that's another question!)