Our English teacher is very picky about our English and American accent.

I can't agree with you on the first floor. Few foreigners are impolite enough to accuse you of poor pronunciation to your face, so you can't know if others laugh at you. English, like other languages, as a tool, its primary function is of course communication, but can you imagine a person who speaks English with a Cantonese accent, saying "Ladies and gentlemen, welcome to China", such as Zhao's "London accent" in a classic sketch, and let them communicate in English? Sure, just slow down and work hard. Sometimes you have to understand a sentence several times. Therefore, pronunciation is by no means a icing on the cake. I really haven't met anyone with excellent pronunciation and confusing grammar words, but I often see people with excellent grammar words and extremely confusing pronunciation, such as English with Indian accent, and many Indians or Indian-Americans can't recognize their pronunciation. If you can't hear clearly, you won't understand, and if you don't understand, it will affect communication. The reason is clear.

American English and English are still very different in pronunciation. Fortunately, the listening level of most foreigners is relatively good, and with the help of context, both old English and old American English can understand each other. But I'm afraid your teacher is inferior to others. I'm not used to listening to your mixed English and American accent. That's his/her personal problem, not Britain or America. American English is the trend now, but it is always a good choice to please the teacher, hehe, choose it yourself.