Translation:You are all American, right?
"you guys are american, right?" was marked correct for me. july 2018.
I submitted this flag: I am a certified English editor. Your alternative answer, "You are all American" is not a correct translation because that English sentence means, "You [singular] are completely American." Your alternative English answer does not mean, "All of you are Americans."
If you use the noun 'American' (an American person), then it takes the plural ending "You are all Americans", like you say. If you use the adjective "American", then there's no need: "These people are American", just like "These people are happy". It is a correct usage. You're right that there's a second meaning to "all American" as in "completely American". That usage gets a hyphen when qualifying a noun: "It is an all-American movie".
I'm sorry, but as an Australian, finishing a question with "..., right?" sounds disgusting. We just don't say that. It's such an American way of asking a question. In this case : "You are all American, aren't you?" would be more natural. If we're going force everyone to speak American, how about "All of y'all are American, right?".... ugh
I would say you would translate it as "both" when there are only two referred to, but "all" for any number of people or things above that. They are both English = there are only two people , they are all English,when there are more. I think dou would apply in both situations.