@JmLee100 so someone suddenly asked me am I from the US? so I wonder why she asked me like that so can I say 내가 영어를 잘해서 그런가? is it because I’m good at English that’s why she thought I’m from the US? this kind of expression
In that kind of situation, I guess "제가 영어를 잘하는 것 같아서 그렇게 말씀하신 거예요?(Do you think I'm fluent in English? And it made you ask like that?)" would work better. I thought you wanted to say that to your friend, but now that I've realized it's someone, I've changed the form of the previous sentence into Korean honorific form.