"Germany is a wealthy country."
Translation:Niemcy to bogaty kraj.
It depends on the country name: https://commons.wikimedia.org/wiki/File:Polish_country_name_genders.svg
Polish has more countries that have plural names: Włochy (Italy), Węgry (Hungary), Indie (India), Chiny (China), not to mention the US and many island countries (which are based on more than one island)... I don't know if there's any logic to it. Well, obviously there is to the US and islands ;)