"Germany is a wealthy country."
Translation:Niemcy to bogaty kraj.
It would be Niemcy są bogatym krajem or Niemcy to jest bogaty kraj, If you do not use "to" you need object in instrumental case.
It depends on the country name: https://commons.wikimedia.org/wiki/File:Polish_country_name_genders.svg
Why is it plural? Is it because of the historical fact that Germany used to be divided to several smaller kingdoms?
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 ;)
" Niemcy są bogatym krajem" - please may I ask, if Niemcy requires są and is plural, then what is the reason why the instrumental adjective and noun "bogatym krajem" is singular?
Although „Niemcy” is plural, it is still just one country. Imagine if you wanted to say "The Germans are a hard-working nation". That's similar story: a plural subject is a singular object.