Hisaさんの話した文章に間違いがあるという前提で、「今私が話した文章はどこが間違ってますか？」と聞くなら、１と２のように言うことができます。
1) Where was the mistake in what I just said?
Where was the mistake...? で「間違いはどこですか？」という聞き方。
2) What was wrong in the sentence I just said?
What was wrong...? で「何が間違ってた？」という聞き方。
もし間違っているか間違っていないかが不明で、「どこか間違っていましたか？」と聞くなら
Did I make a mistake in what I just said?
make a mistake で「間違える」
ご参考になれば幸いです！
If during an online English lesson. after you said something in English - you want to ask where the (grammatical) mistake was in your sentence, you can use the above suggested query.
When learning a new language it is very important to us that our teachers tell us when we make mistakes, using the wrong tense or the incorrect prepositions.
"Grammatical error" or "correct syntax" can be used to find out if your sentence structure was correct. If you used the proper prepositions, adjectives, etc.
Did I make any mistakes in my answer?
Was my syntax use correct?
外国語を学ぶとき、ミス（例えば時制や前置詞の間違いなど）をしたときに先生に指摘してもらうことは非常に重要です。
"Grammatical error" または "Correct syntax" は、構文が間違っていなかったかどうか確認したいときに使うことができます。
Did I make any mistakes in my answer?（文章に間違いはありませんでしたか）
Was my syntax use correct?（構文に間違いはありませんでしたか）
These phrases are both great ways to ask a tutor about a possible error in a sentence. Alternatively, if you feel that your sentence is free of mistakes but could still be improved in terms of style, then you could ask your teacher or tutor something like 'What are the weaknesses in this sentence?' or 'What are some ways I could make this sentence the best it could be?' An example of a stylistic weakness (or lapse) is using 'However,' (instead of 'But') at the beginning of a sentence.
これらは、先生に文中にある間違いについて尋ねるとても良い言い方です。
文に間違いはないだろうけどスタイルについてはまだ改善できると思うなら、例えば次のように尋ねることができます。
'What are the weaknesses in this sentence?'（この文の足らないところはどこですか）
'What are some ways I could make this sentence the best it could be?'（この文で改善できるところはどこですか）
スタイルの改善点（あるいは間違い）というのは例えば、文頭に 'But' でなく 'However' を使うなどです。
"Where in the sentence was an error?" "error" is used rather than mistake, when something isn't right. this sentence is explaining/asking to pin point the error.
"can you point out the mistake in my sentence?" "point out" is an expression used to target or find something in particular ex. "can you point out on the map where we are"
"Where in the sentence was an error?"（この文のどこが間違っていましたか）
= 何かが正しくないときには、'mistake' よりも "error" が使われます。この文では、間違いがどこにあるのか教えて欲しいとお願いしています。
"Can you point out the mistake in my sentence?"（文のどこが間違っていましたか）
= "point out" は「指し示す／具体的な場所を示す」の意味です。
"Can you point out on the map where we are?"
（地図でどこにいるのか指し示してもらえますか）
Please point out the mistake I made in this sentence?
Please let me know where I made a mistake in my sentence?
Can you please tell me what mistake I made in my sentence?
When you have an online lesson, it always good to ask the teacher to type your mistake out for you. Ask the teacher to type what you said and to show you your mistake and then to type it in the correct order. It is easier to learn from your mistake or mistakes when you can see where you made the mistake. It will also be good for you to take it down in your notes so you won't forget it.
日本 
イギリス 
南アフリカ 
アメリカ合衆国 
