"I am an American, and you?"
Translation:Jestem Amerykaninem, a wy?
When I say "jestem amerykanem, a ty" why does it show me the feminin possibility only. Is this a wrong answer for the masculin form? What would be correct?
Nominative: Amerykanin / Amerykanka
Instrumental: Amerykaninem / Amerykanką
So I guess Duo considered your mistake to be closer to "Amerykanką".
"a" is the version of "and" that shows contrast. And here... I'm not sure how to explain it, nothing sounds exactly right.
If you are introducing yourself as an American, it seems very probable that either you are abroad (so your interlocutor is probably from a different country than you), or that you're in America, but you expect your interlocutor to be a foreigner. Anyway, you kind of... expect contrast. And "i" would be used when there's no contrast.
"Ja jestem Amerykaninem, a ty jesteś Włochem" = I am an American, and you are an Italian.
"Ja jestem Amerykaninem i ty też jesteś Amerykaninem" = I am an American and you are an American too. (both sentences seem rather clumsy, but this is the situation when 'i' would make sense).
Doesn't make any sense grammatically. "you" here is another subject (of a clause which works as "And you are... who?"), so it takes Nominative.