When we Japanese use Are you from ?　OOOから、おこしですか? or OOOのかたですか? ex. 東京からおこしですか?　アメリカのかたですか?　we usually guess 000 from their accent or car number plate. Be from is translated as 000の出身です。in a dictionary. But, 出身 mainly means the place where the person was born and grew up. So, we don't say 東京のご出身ですか?(putting ご ) so often. Because it is difficult to guess his hometown. We can only guess his hometown after getting some info. If you are asked アメリカのかたですか? The answer is はい、そうです。You must not say はい、アメリカのかたです。Because かた　is a respect word.

We say it like "何方（どちら）のご出身（しゅっしんですか？" or "何方のお生まれですか？".

You could say "(country)人ですか" to ask if this person is from a country or some other and to answer you could say "はい、(country)人です" and "いいえ、(country)人じゃありません". The "人" word means "person", so with a location, it refers to a population. Thus, "アメリカ人" and "日本人" mean "American" and "Japanese" respectively I hope I can help you with this