If your teacher is American then you will tend to imitate him/her and copy the American accent. Since Chinese is your native language you will always retain your Chinese accent.

I think you have a mixed of both accent. British and US. When you learn and practice , your brain receives it as British accent (you may be learning the British accent). When you actually speak it, the pace is due to you being nervous and the US accent maybe due to your surroundings (you being amongst people who speaks in US accents) So naturally, you will adapt to your surroundings in terms of accent.

My Chinese accent and words change upon who I am talking with. When talking to people in North of China, I use more 兒. When I talk to people in HK, I tend to speak very simply with my Mandarin and a lot slower cause it's not so common for people to understand here, and I use more standard speaking. But, yeah, it depends on who you talk with. My accent for English (my native language) has also changed and changes with who I talk with. When I talk with my parents, I speak very fast and have a Chicago accent, otherwise, now, I have a more Dutch accent when I talk English cause most people I talk with in English are Dutch.

I can also guess where those people from but not now=( but someday I can!The only 2 accent that I can tell the difference is UK and US. By the way I totally understand what u saying but I dont know how to reply u because my god xxxx writing skills:'(

btw, it's good that you can hear the difference. I was with a korean, irish and NZ friends in beijing (it sounds like it should be a joke, but there was no pub involved!), and my korean friend could not tell the difference between Irish and NZ english. It all sounded the same to her.